pie 


tio; 

UN 

Th 

UN 
UN 
UN 


Re 
Pa 
Pn 

AK 
Ni 
Ui. 
N« 


UNIVERSITY  OF  CALIFORNIA 
LOS  ANGELES 


The  RALPH  D.  REED  LIBRARY 


DEPARTMENT  OF  GEOLOGY 

UNIVERSITY  of  CALIFORNIA 


>ES 


ness,  com- 
iture  of  its 
from  the 
ork. 


aker. 


'CS. 

ithematical 


OMKTRV. 
I'RVEYING, 


•WEBSTER'S  DICTIONARIES. 

New  editions  of  the  Primary,  Common  School,  High  School,  Academic  and 
Counting  House  Dictionaries  have  recently  been  issued,  all  of  which  are 
numerously  illustrated. 


Webster's  PRIMARY  SCHOOL  DICTION- 
ARY. 

Webster V  COMMON  SCHOOL  DICTION- 
ARY. 

Webster's  HIGH  SCHOOL  DICTIONARY. 

Webster's  ACADEMIC  DICTIONARY. 

Webster's  COUNTING-HOUSE  AND  FAM- 
ILY DICTIONARY. 


Webster's  POCKET  DICTIONARY.  —  A 
pictorial  abridgment  of  the  quarto. 

Webster's  ARMY  AND  NAVY  DICTION- 
ARY.—Bv  Captain  E.  C.  Bovnton, 
of  West' Point  Military  Academy. 


Ivison,  Blakeman,    Taylor  &  Co,'s  Publications. 

"KERL-S  STANDARD  ENGLISH  GRAMMARS. 

and  completeness,  KERL'S  GRAMMARS 

GRAMMAR.— Designed  for  Schools 
where  only  one  text-book  is  us  id. 


For  more  of  originality,  practicality 
are  recommended  over  others. 
KERL'S  FIRST  LESSONS  IN  GRAMMAR. 
KERL'S  COMMON  SCHOOL  GRAMMAR. 
KERL'S  COMPREHENSIVE  GRAMMAR. 

Recently  issued: 

KBRL'S  COMPOSITION  AND  RHETORIC. — 
A  simple,  concise,  progressive, 
thorough,  and  practical  work  on  a 
new  plan. 

KERL'S   SHORTER   COURSE  IN  ENGLISH 


We  also  fablish  : 

SILL'S  NEW  SYNTHESIS  ;  or,  Elementary 
Grammar. 

SILL'S  BLANK  PARSING  BOOK.— To  ac- 
company above. 

WELLS'  <W.  H.)  SCHOOL  GRAMMAR. 

WELLS'  ELEMENTARY  GRAMMAR. 


GRAY'S    BOTANICAL    TEXT-BOOKS. 


These  standard  text-books  are  recognized  throughout  this  country  and 
Europe  as  the  most  complete  and  accurate  of  any  similar  works  published. 
They  are  more  extensively  used  than  all  others  combined. 

Gray's  MANUAL  WITH  MOSSES,  &c.    Il- 
lustrated. 

FIELD,   FOREST    AND    GARDEN 


Gray's  "  How  PLANTS  GROW." 

Gray's  LESSONS  IN  BOTANY.  302  Draw- 
ings. 

Gray's  SCHOOL  AND  FIELD  BOOK  OF 
BOTANY. 

Gray's  MANUAL  OF  BOTANY,  to  Plates. 

Gray's  LESSOKS  AND  MANI 


ray 


BOTANIST'S  MICROSCOPE. 


Gray's  FIEL 

BOTANY. 
Gray's  STRUCTURAL  'AND  SYSTEMATIC 

BOTANY. 
FLORA  OF  THE  SOUTHERN  STATES, 


2  Lenses. 

3  *' 


WILLSON-'S    HISTORIES. 


Famous  as  being  the  most  perfectly  graded  of  any  before  the  public, 
PRIMARY  AMERICAN  HISTORY. 
HISTORY  OF  THE  UNITED  STVTES. 
AMERICAN  HISTORY.    School  Edition. 
OLTI.INESOFGENERAL  HISTORY.  School 
Edition. 


OUTLINBS  OF  GENERAL  HISTORY.     UnU 

Yersity  Edition. 
WILLSON'S  CHART  OF  AMERICA*   Hi*- 


WELLS'    SCIENTIFIC    SERIES. 


Containing  the   latest  researches  in  Physical   science,  and   their  practical 
application  to  evcry-day  life,  and  is  still  the  best 
SCIENCE  OF  COMMON  THINGS. 
NATURAL  PHILOSOPHY. 
PRiNcirLES  OF  CHEMISTRY. 


. 
FI«ST  PRINCIPLES  OF  GEOLOGY. 


Also: 

Hitchcock's  ANATOMY  AND  PHYSIOLOGY. 
Hitchcock's:  ELEMENTARY  GEOLOGY. 
Eliot  &•  Storer's  CHEMISTRY, 


FASQUELLE'S  FRENCH  COURSE 

Has  had  a  success  snrivaled  in  this  country,  having  passed  through  more 
than  fifty  editions,  and  is  still  the  best. 

Fasquelle's    Introductory    French  Fasquelle's  Dumas'  Napoleon. 

Course.  Fasqutlle's  Racine. 

Larger    French    Course.    Fasquelle's  Manual   of   French    Con- 
nsed.  versation. 

Fasquelle's  Key  to  the  Above.  Ho-wards    Aid   to  French    Compost- 

Fasquelles  Colloquial  French  Reader.  tion. 

Fasquelle's  Telemaque,  Talbef ' s  French  Pronunciation. 


TEXT-BOOK 


GEOLOGY 


DESIGNED  FOR  SCHOOLS  AND  ACADEMIES. 


BY 


JAMES  D.  DANA.,  LL.D., 


PROFESSOR  OF   GEOLOOT  AND  NATURAL  BISTORT  IN  TALK  COLLEGE;  AUTHOR  OP 
"A  MANUAL  OF  GEOLOGY,"  "A  SYSTEM  OF  MINERALOGY,"  OF  REPORTS 
""   WILKES'S  EXPLORING  EXPEDITION  ON  GEOLOGY,  ZOOPHYTES, 
CRUSTACEA,   ETC. 


ILL03TKATED  B\  375  AOOO  CUTS. 


IVISOX,  BLAKEMAN,   TAYLOR,  &  COMPANY, 
NEW  YORK  AND  CHICAGO. 


Manual  of  Geology:  treating;  cf  the  Principles  of  the  Science,  with  special 
reference  to  American  Geological  llistory.  By  JAMES  D  DANA,  M.A.,  LL.D.  Illus- 
trated by  a  Chart  of  the  World,  and  over  one  thousand  figures,  mostly  from  Ameri- 
can sources. 

814  pages,  8vo.    Muslin 55.00 

"  "       Half  Turkey  morocco 6.00 

Principles  of  Physics  ;  or,  Natural  Philosophy.    Designed  for  the  •  ie 
of  Colleges  and   Schools.    By   BENJAMIN  SILLIMAN,   JR.,   M.A.,  M.D ,  Professor  of 
Chemistry  in  Yalo  College.    With  seven  hundred  and  twenty-two  illustrations. 
710  pagos,  small  Svo 3.50 

First  Principles  of  Chemistry.    For  the  use  of  Colleges  and  Schools.    By 
Prof.  B.  SILLIMAN,  Jr. 
554  pages,  12mo 2.00 


Entered,  according  to  Act  of  Congress,  in  the  year  1863,  by 
THEODORE  BLISS  &  CO. 

In  the  Clerk's  Office  of  the  District  Court  of  the  United  States  for  the  Eastern 
District  of  Pennsylvania. 


PREFACE. 


IN  preparing  this  abridgment  of  my  Manual  of  Geology, 
the  arrangement  of  the  larger  work  has  been  retained.  The 
science  is  not  made  a  dry  account  of  rocks  and  their  fossils, 
but  a  history  of  the  earth's  continents,  seas,  strata,  moun- 
tains, climates,  and  living  races;  and  this  history  is  illus- 
trated, as  far  as  the  case  admits,  by  means  of  American  facts, 
without,  however,  overlooking  those  of  other  continents,  and 
especially  of  Great  Britain  and  Europe. 

No  glossary  of  scientific  terms  has  been  inserted,  because 
the  volume  is  throughout  a  glossary,  or  a  book  of  explana- 
tions of  such  terms,  and  it  is  only  necessary  to  refer  to  the 
Index  to  find  where  the  explanations  are  given. 

The  teacher  of  Geology,  and  the  student  who  would 
extend  his  inquiries  beyond  his  study  or  recitation-room,  is 
referred  to  the  "  Manual"  for  fuller  explanations  of  all  points 
that  come  under  discussion  in  the  "  Text-book, — including  a 
more  complete  survey  of  the  rock-formations  of  America 
and  other  parts  of  the  world,  with  many  sections  and  details 
of  local  geology, — a  much  more  copious  exhibition  of  the 
ancient  life  of  the  several  epochs  and  periods  and  of  the 
principles  deduced  from  the  succession  of  living  species  on 
the  globe, — a  more  thorough  elucidation  of  the  departments 
of  Physiographic  and  Dynamical  Geology, — a  chapter  on 
the  Mosaic  Cosmogony, — a  large  number  of  additional  wood- 
cut illustrations,  and  references  to  authorities,  with  personal 
acknowledgments,  besides  a  general  chart  of  the  world. 

NEW  HAVEN,  CT.,  December  1,  1S63. 


490706 


TABLE  OF  CONTENTS. 


RAM 

INTRODUCTION 1 

PAET  I.— Physiographic  Geology. 

1.  General  Characteristics  of  the  Earth's  Features 5 

2.  System  in  the  Earth's  Features 8 


PAET  II,— Lithological  Geology 


1.  CONSTITUTION  OF  ROCKS 14 

1.  General  Observations  on  their  Constituents 14 

2.  Kinds  of  Rocks 20 

2.  CONDITION,  STRUCTURE,  AND  ARRANGEMENT  OF  ROCK-MASSES 27 

Stratified  Condition 31 

1.  Structure 31 

2.  Positions  of  Strata 36 

3.  Order  of  Arrangement  of  Strata 43 

REVIEW  OF  THE  ANIMAL  AND  VEGETABLE  KINGDOMS. 

1.  Animal  Kingdom 48 

2.  Vegetable  Kingdom 60 

PAET  III.— Historical  Geology. 

General  Observations 63 

I.  AZOIC  TIME  OR  AGE 72 

II.  PALEOZOIC  TIME 78 

I.  AGE  OF  MOLLUSKS,  OR  SILURIAN  AGE 73 

1.  Primordial  or  Potsdam  Period 79 

2.  Trenton  and  Hudson  Periods 85 

3.  Upper  Silurian  Era. 94 

iv 


CONTENTS.  V 

II.  PALEOZOIC  TIME—  (continued).  PAGB 

II.  AGE  OF  FISHES,  OB  DEVONIAN  AGE  ....................................  104 

III.  AGE  or  COAL  PLANTS,  OR  CARBONIFEROUS  AGE  ..................  116 

GENERAL  OBSERVATIONS  ON  THE  PALEOZOIC  ...........................  142 

DISTURBANCES  CLOSING  PALEOZOIC  TIME  ................................  154 

III.  MESOZOIC  TIME  ..................................................................  162 

REPTILIAN  AGE  .........................  ,  ..........................................  163 

1.  Triassic  and  Jurassic  Periods  ........................................  164 

2.  Cretaceous  Period  .......................................................  188 

GENERAL  OBSERVATIONS  ON  THE  MESOZOIC  ERA  .....................  198 

DISTURBANCES  AND  CHANGES  OF  LEVEL  CLOSING  MESOZOIC  TIME  202 

IV.  CENOZOIC  TIME  ..................................................................  205 

MAMMALIAN-  AGE  .................................................................  205 

1.  Tertiary  Period  ...........................................................  20« 

2.  Post-tertiary  Period  ....................................................   219 

1.  Glacial  Epoch  ....................  TT.  ..............................  220 

2.  Champlain  Epoch  ..................................................  224 

3.  Terrace  Epoch  ......................................................  227 

3.  Life  of  the  Post-tertiary  ..............................................  229 

GENERAL  OBSERVATIONS  ON  CENOZOIC  TIMS  ............................  234 

V.  ERA  OF  MIND—  AGE  OF  MAN  .............................................  236 

GBNERAL  OBSERVATIONS  ON  GEOLOGICAL  HISTORY  .....................  243 

PAET  IT—  Dynamical  Geology, 

I.  LIFE  ......................................................................................  262 

1.  Peat  Formations  ...............................................................  263 

'2,  Beds  of  Microscopic  Organisms  ...........................................  265 

3.  Coral  Reefs  ......................................................................  266 

II.  THE  ATMOSPHERE  ....................................................................  271 

III.  WATER  ...................................................................................  273 

1.  Fresh  Waters  ....................................................................  273 

2.  The  Ocean  .......................................................................  283 

3.  "Freezing  and  Frozen  Waters,  Glaciers,  Icebergs  .....................  290 

4.  Formation  of  Sedimentary  Strata  ........................................  296 


IV.  HE^T  .....................................................................................  299 

1.  Heat  of  the  Globe  .............................................................  299 

2.  Volcanoes  and  Non-volcanic  Igneous  Ejections  ......................  301 

3.  Metamorphism  and  Origin  of  Veins  .....................................  312 

4.  Movements  in  the  Earth's  Crust  ..........................................  318 


V  CONTENTS. 

IV.  HEAT — (continued).  PAG» 

Movements  of  the  Earth's  Crust. 

1.  Plications,  Mountains 318 

2.  Joints — Slaty  Cleavage 323 

3.  Earthquakes 324 

4.  Origin  of  the  Earth's  General  Features 326 

V.  COSCLTTSIOX. ....* •*•*... 336 

APPENDIX. 

1.  Catalogue  of  American  Localities  of  Fossils 341 

2.  Mineralogical  Implements,  etc 344 

INDEX...,  .......    - .....349 


INTRODUCTION. 


1.  Rock-structure  of  the  earth's  crust. — Beneath  the  soil 
and  waters  of  the  earth's  surface  there  is  everywhere  a  base- 
ment of  rocks.  The  rocky  bluffs  forming  the  sides  of  many 
valleys,  the  ledges  about  the  tops  of  hills  and  mountains,  and 
the  cliffs  along  sea-shores,  are  portions  of  this  basement 
exposed  to  view. 

The  rocks  generally  lie  in  beds;  and  these  beds  vary  from 
a  few  feet  to  hundreds  of  yards  in  thickness.  The  different 
kinds  are  spread  out  one  over  another,  in  many  alternations. 
Sometimes  they  are  in  horizontal  layers;  but  very  often 
they  are  inclined,  as  if  they  had  been  pushed  or  thrown  out 
of  their  original  position;  and  in  some  regions  they  are 
crystallized.  Moreover,  they  are  not  all  found  in  any  one 
country. 

By  careful  study  of  the  rocks  of  different  continents,  it 
has  been  ascertained  that  the  series  of  beds,  if  all  were  in 
one  pile,  would  have  a  thickness  of  15  or  18  miles.  The 
actual  thickness  in  most  regions  is  far  less  than  this. 

These  15  or  18  miles  out  of  the  4000  miles  between  the 
earth's  surface  and  centre  are  all  of  the  great  sphere  that 
are  within  reach  of  observation. 

The  series  of  rocks  alluded  to  overlie,  beyond  all  question, 
crystalline  rocks  that  are  not  part  of  the  series.  There  is 
good  reason  for  believing,  also,  that,  not  many  scores  of 
miles  below  the  surface,  the  whole  interior  of  the  globe  is 
in  a  melted  state.  These  fiery  depths  are  nowhere  open  to 
examination ;  yet  the  rocks  ejected  in  a  melted  state  from 


2  INTRODUCTION. 

volcanoes  or  from  the  earth's  fissures  are  supposed  to  afford 
indications  of  what  they  contain. 

2.  Facts  taught  by  the  arrangement  and  structure  of  the  rocks. 
—The  various  rocks  afford  proof  that  they  were  all  slowly  or 
gradually  made, — the  lowest  in  the  series,  of  course,  first, 
and  so  on  upward  to  the  last.  The  lowest,  therefore,  belong 
to  an  early  period  of  the  world,  and  those  above  to  later 
periods,  in  succession. 

Some  of  the  beds  indicate,  by  evidence  that  cannot  be 
doubted,  that  they  were  made  over  the  bottom  of  a  shallow 
ocean,  like  the  muddy  and  sandy  deposits  on  soundings ; 
or  along  the  ocean's  borders,  like  the  accumulations  of  a 
beach,  or  of  a  salt-marsh;  others, that  they  were  formed  by 
tne  action  of  the  waters  of  lakes,  or  of  rivers ;  and  others 
still,  that  they  were  gathered  together  by  the  drifting  of  the 
winds,  as  sands  are  drifted  and  heaped  up  near  various  sea- 
coasts.  In  many  of  the  rocks  there  are  marks  on  the  layers 
that  were  made  by  the  rippling  waves  or  the  currents  when 
the  material  of  the  bed  was  loose  sand  or  clay ;  or  there  are 
cracks — though  now  filled— that  were  opened  by  the  drying 
sun  in  an  exposed  mud-flat;  or  impressions  produced  by  the 
drops  of  a  fall  of  rain. 

In  some  regions  the  beds,  after  being  consolidated,  have 
been  profoundly  fractured,  and  the  fissures  thus  opened  were 
often  filled  at  once  with  rock,  in  a  melted  state,  proceeding 
from  the  depths  below.  Again,  they  have  been  uplifted  or 
pressed  into  great  folds,  and  mountain-ranges  have  some- 
times been  made  as  a  consequence  of  the  upturning ;  and,  in 
addition,  they  have  often  undergone  crystallization  over  a 
country  thousands  or  even  hundreds  of  thousands  of  square 
miles  in  area. 

The  succession  of  rocks  in  the  earth's  crust  is,  hence,  like 
a  series  of  historical  volumes,  and  full  of  inscriptions.  It  is 
the  endeavor  of  Geology  to  examine  and  interpret  these 
inscriptions.  They  are  sufficient,  if  faithfully  studied  and 


INTRODUCTION.  3 

compared,  to  make  known  the  general  condition  of  the  con- 
tinents and  seas  in  the  course  of  the  world's  progress,  and 
also  to  tell  of  the  epochs  of  disturbance  or  revolution,  and 
of  mountain-making. 

3.  Facts  taught  by  the  fossil  contents  of  rocks. — Again, 
most  of  the  beds  contain  shells,  corals,  and  other  related 
forms,  called  fossils. — so  named  because  dug  out  of  the  earth, 
the  word  being  from  the  Latin  fossilis,  meaning,  that  which 
is  dug  up.     These  fossils  are  the  remains  of  living  animals 
that  once  inhabited  the  earth.     The  shells  and  corals  were 
formed  by  animals,  just  as  the  shell  of  a  clam  is  now  formed 
by  the  animal  occupying  it,  or  corals  of  existing  seas  by  the 
coral  animals.     The  various  species  that  have  left  their  re- 
mains in  any  bed  must  have  been  in  existence  when  that 
bed  was  in  progress  of  formation :   they  were  the  living 
species  of  the  waters  and  land  at  the  time. 

The  fossils  that  occur  in  one  bed  differ  in  species  entirely, 
or  nearly  so,  from  those  of  every  other  bed  in  the  series. 
In  other  words,  each  bed  has  its  own  peculiar  species,  those 
of  the  bottom  almost  or  wholly  unlike  those  in  the  one  next 
above ;  and  those  of  this  bed  as  much  unlike  those  of  the 
following;  and  so  on.  Since,  therefore,  each  bed  contains 
evidence  as  to  what  animals  and  plants  were  living  when  it 
was  forming,  the  study  of  the  fossils  of  the  successive  beds 
is  the  study  of  the  succession  of  living  species  that  have 
existed  in  the  earth's  history. 

4.  Objects  of  Geology,  and  Subdivisions  of  the  science. — 
The  preceding  explanations  aiford  an  idea  of  the  objects  of 
the  science  of  Geology.     They  are — 

(1.)  To  study  out  the  system  in  the  earth's  features. 

(2.)  To  ascertain  the  nature  and  arrangement  of  the  rocks. 

(3.)  To  make  out  the  true  history,  or  succession  of  events, 
as  to  the  formation  of  rocks,  the  production  of  the  features 
of  the  surface  and  the  disturbances  of  rocks,  and  the  progress 
and  all  changes  in  the  living  species  of  the  globe. 


4  INTRODUCTION. 

(4.)  To  determine  the  causes  of  all  that  has  happened  in 
the  earth's  history,  that  it  may  be  understood  how  rocks 
•were  made,  fractured,  uplifted,  folded,  and  crystallized ;  how 
mountains  were  made,  and  valleys,  and  rivers;  how  con- 
tinents and  oceanic  basins  were  made,  and  how  altered  in 
size  or  outline  from  period  to  period ;  why  the  climate  of 
the  globe  changed  from  time  to  time ;  and  how  the  living 
species  of  the  globe  were  exterminated,  or  otherwise  affected 
by  the  physical  changes  in  progress. 

There  are,  hence,  four  principal  branches  of  the  science : — 

1.  PHYSIOGRAPHIC  GEOLOGY, — treating  of  the  earth's  phy- 
sical features;  that  is,  of  the  system  in  the  exterior  features 
of  the  earth.     (This  department  properly  includes,  also,  the 
system  of.  movements  in  the  water  and  atmosphere,  and  the 
system  in  the  earth's  climates,  and  in  the  other  physical 
agencies  or  conditions  of  the  sphere.) 

2.  LITHOLOGICAL  GEOLOGY, — treating  of  the  rocks  of  the 
globe,  their  kinds,  structure,  and   conditions  or  modes  of 
occurrence.     The  word  lithological  is  from  the  Greek  lithos, 
stone,  and  logos,  discourse. 

3.  HISTORICAL  GEOLOGY, — treating  of  the  succession  in 
the  rocks  of  the  globe,  and  their  teachings  with  regard  to 
the  successive  conditions  of  the  earth,  or  to  the  changes  in 
its  oceans,  continents,  climates,  and  life. 

4.  DYNAMICAL  GEOLOGY, — treating  of  the  causes,  or  the 
methods,  by  which  the  rocks  were  made,  and  by  which  all 
the  earth's  changes  were  brought  about.      The  word  dy- 
namical is  from  the  Greek  dunamis,  power  or  force. 

These  causes  have  acted  through  the  sustaining  power 
and  guidance  of  the  great  Cause  of  causes,  the  Infinite 
Creator,  who  made  matter  and  all  the  kinds  of  life,  and 
who  has  ever  directed  and  still  directs  in  every  passing 
event 


PART  I. 

PHYSIOGRAPHIC  GEOLOGY. 


UNDER  the  department  of  Physiographic  Geology  only  a 
brief  and  partial  review  is  here  made  of  the  general  features 
of  the  earth's  surface. 

THE   EARTH'S  FEATURES. 
1.  GENERAL  CHARACTERISTICS. 

1.  Size  and  form. — The  earth  has  a  circumference  of  about 
25,000  miles.     Its  form  is  that  of  a  sphere  flattened  at  the 
poles,  the  equatorial  diameter  (7926  miles)  being  a-bout  13 k 
miles  greater  than  the  polar. 

2.  Oceanic  basin  and  continental  plateaus. — Nearly  three- 
fourths  (more  accurately,  eight-elevenths*)  of  the  whole  surface 
are  depressed  below  the  rest  and  occupied  by  salt  water. 
This  sunken  part  of  the  crust  is  called  the  oceanic  basin,  and 
the  large  areas  of  land  between,  the  continents,  or  continental 
plateaus. 

3.  Subdivisions  and  relative  positions  of  the  oceanic  basin  and 
continental  plateaus. — Nearly  three-fourths  of  the  area  of  the 
continental  plateaus  are  situated  in  the  northern  hemisphere, 
and  more  than   three-fourths  of  the   oceanic   basin   in   the 
southern  hemisphere.      The   dry  land   may  be  said   to  be 
clustered  about  the  North  pole,  and  to  stretch  southward 
in  two  masses,  an  Oriental,  including  Europe,  Asia,  Africa, 
and  Australasia,   and    an   Occidental,  including   North  and 


0  PHYSIOGRAPHIC  GEOLOGY. 

South  America.  The  ocean  is  gathered  in  a  similar  manner 
about  the  South  pole,  and  extends  northward  in  two  broad 
areas  separating  the  Occident  and  Orient,  namely,  the 
Atlantic  and  Pacific  Oceans,  and  also  in  a  third,  the  Indian 
Ocean,  separating  the  southern  prolongations  of  the  Orient, 
namely,  Africa  and  Australasia. 

The  Orient  is  made,  by  this  means,  to  have  two  southern 
prolongations,  while  the  Occident,  or  America,  has  but  one. 
This  double  feature  of  the  Orient  accords  with  its  great 
breadth ;  for  it  averages  6000  miles  from  east  to  west,  which 
is  far  more  than  twice  the  breadth  of  the  Occident  (2200  miles). 

The  inequality  of  the  two  continental  masses  has  its 
parallel  in  the  inequality  of  the  Pacific  and  Atlantic  Oceans; 
for  the  former  (6000  miles  broad)  is  more  than  double  the 
average  breadth  of  the  latter  (2800  miles).  Thus  there  is  one 
broad  and  one  narrow  continental  mass,  and  one  broad  and  one 
narrow  oceanic  area. 

The  connection  of  Asia  with  Australia,  through  the  inter- 
vening islands,  is  very  similar  to  that  of  North  America  with 
South  America.  The  southern  continent,  in  each  case,  lies 
almost  wholly  to  the  east  of  the  meridians  of  the  northern ; 
and  the  islands  between  are  nearly  in  corresponding  posi- 
tions,— Florida  in  the  Occident  corresponding  to  Malacca 
in  the  Orient,  Cuba  to  Sumatra,  Porto  Rico  to  Java,  and 
the  more  eastern  Antilles  to  Celebes  and  other  adjoining 
islands.  It  is,  therefore,  plain  that  Australia  bears  the  same 
relation  to  Asia  that  South  America  does  to  North  America. 
It  is  also  true  that  Africa  is  essentially  in  a  similar  position 
with  reference  to  Europe. 

The  northern  portion  of  the  Orient,  or  Europe  and  Asia 
combined,  makes  one  continental  area ;  and  its  general  course 
is  east  and  west.  The  northern  portion  of  the  Occident,  or 
North  America,  is  elongated  from  north  to  south. 

4.  Oceanic  depression  and  continental  elevations. — The  depth 
of  the  oceanic  basins  below  the  water-level  is  probably  in 


THE  EARTH'S  FEATURES.  .7 

some  parts  50,000  feet.  The  mean  depth  is  much  less.  The 
depth  across  from  Newfoundland  to  Ireland,  along  what  is 
called  the  telegraphic  plateau,  is  from  10,000  to  15,000  feet. 
Farther  south,  the  Atlantic  Ocean  is  undoubtedly  very 
much  deeper;  but  the  soundings  hitherto  made  are  not 
trustworthy  as  to  the  exact  depth.  The  mean  depth  of  the 
north  Pacific  between  Japan  and  San  Francisco  has  been 
determined  by  Professor  Bache,  from  the  passage  of  earth- 
quake-waves in  1855,  to  be  13,000  feet.  This  is  the  narrower 
part  of  the  Pacific  Ocean,  and  is  probably  much  less  deep 
than  that  in  the  southern  hemisphere. 

The  highest  point  of  the  continents  that  has  been  mea- 
sured is  29,000  feet :  it  is  the  peak  called  Mount  Everest,  in 
the  Himalayas.  But  the  mean  height  of  the  continental 
plateaus  is  only  about  1000  feet.  The  mean  height  of  the 
several  continents  has  been  estimated  as  follows :  Of 
Europe,  670  feet;  Asia,  1150  feet;  North  America,  748  feet; 
South  America,  1132  feet;  all  America,  932  feet;  Europe 
and  Asia,  1000  feet;  Africa,  probably  1600  feet;  and  Aus- 
tralia, perhaps  500.  The  material  in  the  Pyrenees,  if  spread 
equally  over  Europe,  would  raise  the  surface  only  6  feet; 
and  that  of  the  Alps,  only  22  feet.  Although  some  moun- 
tain-chains reach  to  a  great  elevation,  their  breadth  above 
a  height  of  1000  feet  is  small  compared  with  that  of  the 
continents  below  this  height. 

5.  True  outline  of  the  oceanic  depression. — Along  the  oceanic 
borders  the  sea  is  often,  for  a  long  distance  out,  quite  shal- 
low, because  the  continental  lands  continue  on  under  water 
with  a  nearly  level  surface;  then  comes  a  rather  sudden 
slope  to  the  deep  bed  of  the  ocean.  This  is  the  case  off  the 
eastern  coast  of  the  United  States,  south  of  New  England. 
Off  New  Jersey,  the  deep  water  begins  along  a  line  about 
80  miles  from  the  shore;  off  Virginia,  this  line  is  50  to  60 
miles  at  sea;  and  thus  it  gradually  approaches  the  coast  to 
the  southward.  The  slope  of  the  bottom  for  the  80  milea 
2 


8  PHYSIOGRAPHIC   GEOLOGY. 

off  New  Jersey  is  only  1  foot  in  700  feet.  The  true  bound- 
ary between  the  continental  plateau  and  the  oceanic  depres- 
sion is  the  commencement  of  the  abrupt  slope.  The  British 
Islands  are  situated  on  a  submerged  portion  of  the  European 
continent,  and  are  essentially  a  part  of  that  continent,  the 
limit  of  the  oceanic  basin  being  far  outside  of  Ireland,  and 
extending  south  into  the  Bay  of  Biscay.  New  Guinea  is  in 
a  similar  way  proved  to  be  a  part  of  Australia. 

6.  Surfaces  of  the  continents. — The  surface  of  a  continent 
comprises  (1)  low  lands,  (2)  high  or  elevated  plateaus  or  table- 
lands, and  (3)  mountain-ridges.  The  mountain-ridges  may 
rise  either  from  the  low  lands  or  the  plateaus.  The  plateaus 
are  great  areas  of  the  surface  situated  several  hundred  feet, 
or  a  thousand  feet  or  more,  above  the  sea,  or  above  the 
general  level  of  the  low  lands.  They  are  often  a  part  of 
the  great  mountain-chains.  Sometimes  plateaus  include  a 
region  between  mountain-ridges,  and  sometimes  the  mass 
of  the  mountains  themselves  out  of  which  the  ridges  rise. 
For  example,  the  regions  of  northern  and  southern  New 
York  are  plateaus  (the  former  averaging  1500  feet  in  height, 
the  latter  2000  feet)  situated  within,  or  on  the  borders  of,  the 
Appalachian  chain.  The  eastern  part  of  New  Mexico  is  a 
plateau  about  4000  feet  above  the  sea,  called  the  Llano  esta- 
cado,  and  Mexico  is  situated  in  another  plateau,  from  which 
rise  various  ridges  and  peaks ;  and  both  of  these,  besides 
others,  are  situated  in  the  region  of  the  Rocky  Mountain 
chain,  or  the  great  western  chain  of  North  America.  The 
Desert  of  Gobi,  between  the  Altai  and  the  Kuen-Luen  range, 
is  a  desert  plateau  about  4000  feet  high.  Persia  and  Ar- 
menia constitute  another  plateau.  These  examples  are  suffi- 
cient to  explain  the  use  of  the  term. 

2.  SYSTEM  IN  THE  EARTH'S  FEATURES. 

1.  General  form  of  the  continents  resulting  from  their  reliefs. — 
The  continents  are  constructed  on  a  common  model,  as 


THE  EARTH'S  FEATURES.  9 

follows  :  they  have  high  borders  and  a  low  centre,  and  are,  there- 
fore, basin-shaped.  Thus,  North  America  has  the  Appala- 
chians on  the  eastern  border,  the  Eocky  chain  on  the  west, 
and  between  these  the  low  Mississippi  basin.  Fig.  1  illus- 

Fig.  1. 


trates  this  form  of  the  continent.  In  the  section,  b  repre- 
sents the  Eocky  Mountain  chain  on  the  west,  with  its  double 
line'of  ridges  at  summit;  a,  the  Washington  chain  (including 
the  Sierra  Nevada  and  Cascade  range)  near  the  Pacific 
coast;  c,  the  Mississippi  basin;  d,  the  Appalachian  chain  on 
the  east. 

South  America,  in  a  similar  manner,  has  the  Andes  on 
the  west,  the  Brazilian  Mountains  on  the  east,  and  other 
heights  along  the  north,  with  the  low  region  of  the  Amazon 
and  La  Plata  making  up  the  larger  part  of  the  great  inte- 
rior. Fig.  2  is  a  transverse  section  from  west  to  east 

Fig.  2. 

A  A 


(W,  E),  showing  the  Andes  at  a  and  the  Brazilian  Moun- 
tains at  b.  In  these  sections  the  height  as  compared  with 
the  breadth  is  necessarily  much  exaggerated. 

In  the  Orient,  there  are  mountains  on  the  Pacific  side, 
others  on  the  Atlantic;  and,  again,  the  Himalayas  on  the 
south  face  the  Indian  Ocean,  and  the  Altai  face  the  Arctic 
or  Northern  Seas.  Between  the  Himalayas  (or  rather  the 
Kuen-Luen  Mountains,  which  are  just  north)  and  the  Altai 


10  PHYSIOGRAPHIC   GEOLOGY. 

lies  the  plateau  of  Gobi,  which  is  low  compared  with  the 
enclosing  mountains;  and  farther  west  there  are  the  low 
lands  of  the  Caspian  and  Aral,  the  Caspian  lying  even  below 
the  level  of  the  ocean.  The  Urals  divide  the  6000  miles  of 
breadth  into  two  parts,  and  so  give  Europe  some  title  to  its 
designation  as  a  separate  continent.  West  of  their  meri- 
dian there  are  again  extensive  low  lands  over  middle  and 
southern  European  Russia. 

In  Africa,  there  are  mountains  on  the  eastern  border,  and 
on  the  western  border  south  of  the  coast  of  Guinea;  there 
are  also  the  Atlas  Mountains  along  the  Mediterranean,  and 
the  Kong  Mountains  along  the  Guinea  coast;  and  the  inte- 
rior is  relatively  low,  although  mostly  1000  to  2000  feet  in 
elevation. 

In  Australia,  also,  there  are  high  lands  on  the  eastern 
and  western  borders,  and  the  interior  is  low. 

All  the  continents  are,  therefore,  constructed  on  the  basin- 
model.  ^, 

2.  Relation  between  the  heights  of  the  borders  and  the  extent 
of  the  adjoining  ocean. — There  is  a  second  great  truth  with 
regard  to  the  continental  reliefs;  namely,  that  the  highest 
border  faces  the  largest  ocean. 

By  largest  ocean  is  meant  not  merely  greatest  in  surface, 
but  greatest  in  capacity,  the  depth  being  important  in  the 
consideration.  The  Pacific,  both  in  depth  and  surface,  greatly 
exceeds  the  Atlantic ;  so  the  South  Pacific  exceeds  the 
North  Pacific  and  the  South  Atlantic  exceeds  the  North  At- 
lantic. The  Indian  Ocean  is  also  one  of  the  large  oceans; 
for  it  extends  eighty  degrees  of  latitude  south  of  Asia  before 
reaching  any  body  of  Antarctic  land ;  and  this  is  equivalent 
to  5500  miles,  nearly  the  mean  breadth  of  the  Pacific  :  more- 
over, as  it  is  much  more  free  from  islands  than  the  Pacific, 
it  is  probably  the  deeper  of  the  two,  and,  consequently,  yields 
in  capacity  to  no  other  ocean  on  the  globe. 

Each  of  the   continents   sustains  the   truth   announced. 


THE  EARTH'S  FEATURES.  H 

North  America  has  its  great  mountains,  the  Eocky  chain, 
on  the  side  of  the  great  ocean,  the  Pacific;  and  its  small 
mountains,  the  Appalachian,  on  the  side  of  the  small  ocean. 
So,  South  America  has  its  highest  border  on  the  west;  and 
the  Andes  as  much  exceed  in  elevation  and  abruptness  the 
Eocky  chain  as  the  South  Pacific  exceeds  in  capacity  the 
North  Pacific.  The  Orient  has  high  ranges  of  mountains 
on  the  east,  or  the  Pacific  side,  and  lower,  as  those  of  Norway 
and  other  parts  of  Europe,  on  the  west;  and  the  Himalayas, 
the  highest  of  the  globe,  face  the  great  Indian  Ocean  (besides 
being  most  elevated  eastward  towards  the  great  Pacific), 
while  the  smaller  Altai  face  the  small  Northern  Ocean.  In 
Africa  the  eastern  mountains,  or  those  on  the  Indian  Ocean 
side,  are  higher  than  those  on  the  Atlantic.  In  Australia 
the  highest  border  is  on  the  Pacific  side;  for  the  South 
Pacific,  taking  into  view  its  range  in  front  of  east  Austra- 
lia, is  greater  than  the  Indian  Ocean  fronting  west  Aus- 
tralia. 

Hence  the  basin-shape,  before  illustrated,  is  that  of  a 
basin  with  one  border  much  higher  than  the  other,  and  the 
highest  border  the  one  that  adjoins  the  largest  ocean. 

These  features  have  a  vast  influence  in  adapting  the  con- 
tinents for  man. 

America  stands  with  its  highest  border  in  the  far  west, 
and  with  all  its  great  plains  and  great  rivers  inclined 
towards  the  Atlantic;  for  through  the  Gulf  of  Mexico  the 
whole  interior,  as  well  as  the  eastern  border,  has  its  natural 
outlet  eastward.  Had  the  high  mountains  of  the  continent 
been  placed  on  its  eastern  side,  they  would  have  condensed 
the  moisture  of  the  winds  before  they  had  traversed  the 
land,  and  sent  it  back,  in  hurrying  and  almost  useless  tor- 
rents, to  the  ocean;  but,  being  on  the  western,  all  the  slopes 
from  the  Atlantic  to  the  tops  of  the  Eocky  Mountains  lie 

2* 


12  PHYSIOGRAPHIC   GEOLOGY. 

open  to  the  moist  winds,  and  fields  and  rivers  show  the 
good  they  thus  receive. 

Again,  the  Orient,  instead  of  rising  into  Himalayas  on  the 
Atlantic  border,  has  its  great  heights  in  the  remote  east, 
and  its  vast  plains  and  the  larger  part  of  its  great  rivers, 
even  those  of  central  Asia,  have  their  natural  outlet  west- 
ward, or  towards  the  same  Atlantic  Ocean.  Thus,  as  Pro- 
fessor Guyot  has  said,  the  vast  regions  of  the  world  which 
are  best  fitted  by  climate  and  productions  for  man  are  com- 
bined into  one  great  arena  for  the  progress  of  civilization. 
Both  the  Orient  and  the  Occident  pour  their  streams  and 
bear  a  large  part  of  their  commerce  into  a  common  ocean ; 
and  this  ocean,  the  Atlantic,  is  but  a  narrow  ferriage  between 
them,  and  vastly  better  for  the  union  of  nations  than  con- 
nection by  as  much  dry  land  :  3000  miles  of  dry  land  would 
be,  even  in  the  present  age,  a  serious  obstacle  to  intercourse ; 
while  3000  miles  of  ocean  draw  the  east  and  west  only  into 
closer  political,  commercial,  and  social  relations. 


PART  H. 

LITHOLOGICAL  GEOLOGY. 


THE  term  rock,  in  geology,  is  applied  to  all  natural  forma- 
tions of  rock-material,  whether  solid  or  otherwise.  Not 
only  are  sandstones  and  slates  called  rocks,  but  also 
the  loose  earth,  sand,  and  gravel  of  the  surface,  provided 
they  have  been  laid  out  in  beds  by  natural  causes.  All 
sandstones  were  once  beds  of  loose  sand ;  and  there  is  every 
shade  of  gradation  from  the  hardest  sandstone  to  the  softest 
sand-bed :  so  that  it  is  impossible  to  draw  a  line  between 
the  consolidated  and  unconsolidated.  Geology  does  not 
attempt  to  draw  the  line,  but  classes  all  together  as  rocks, 
regarding  consolidation  as  an  accident  that  might  or  might 
not  happen  in  the  case  of  the  earth's  beds  or  deposits. 

Rocks  may  be  studied  simply  as  rocks, — that  is,  with 
reference  to  their  composition, — and  collections  may  be  made 
containing  specimens  of  their  various  kinds.  Again,  they 
may  be  studied  as  rock-masses  spread  out  over  the  earth 
and  forming  the  earth's  crust;  and,  with  this  in  view,  the 
condition,  structure,  and  arrangement  of  the  great  rock- 
masses  (called  sometimes  terrains')  would  come  up  for  con- 
sideration. The  two  subjects  under  Lithological  Geology 
are,  therefore :  (1.)  The  constitution  of  rocks ;  (2.)  The  condi- 
tion, structure,  and  arrangement  of  rock-masses. 

13 


14  LITHOLOGIOAL   GEOLOGY. 

1.  CONSTITUTION  OF  ROCKS. 
1.  GENERAL  OBSERVATIONS  ON  THEIR  CONSTITUENTS. 

Eocks  consist  essentially  of  mineral  material.  The  fol- 
lowing are  the  most  common  kinds. 

1.  Quarts,  or  Silica. — Quartz,  or,  as  it  is  called  in  chemistry, 
silica,  far  exceeds  all  other  species  in  abundance.  It  is  ono 
of  the  hardest  of  minerals;  it  does  not  melt  before  the  blow- 
pipe, and  does  not  dissolve  in  water.  Its  hardness  and 
durability  especially  fit  it  for  this  place  of  first  import- 
ance in  the  material  of  the  earth's  foundations. 

It  often  occurs  in  crystals  of  the  forms  represented  in 
figs.  3,  4,  though  generally  occurring  in  grains,  pebbles, 
or  masses.  It  is  distinguished  ordina-  j?j  3  Fi  4 
rily  by  its  glassy  aspect,  whitish  or 
grayish  color,  and  an  absence  of  all 
tendency  to  break  with  a  smooth  sur- 
face of  fracture  (a  quality  of  crystals 
called  cleavage).  Although  usually  nearly 
colorless  or  white,  it  is  very  often  red- 
dish, yellowish,  brownish  (especially  smoky  brown),  and 
even  black;  and  the  lustre  is  sometimes  very  dull,  as  in 
chalcedony,  flint,  and  jasper.  The  sands  and  pebbles  of  tho 
sea-shores  and  gravel-beds  are  mostly  quartz, — because 
quartz  resists  the  wearing  action  of  waters  better  than  any 
other  common  mineral.  For  the  same  reason,  most  sand- 
stones and  conglomerates  consist  mainly  of  quartz. 

Tho  hardness  (on  account  of  Avhich  it  scratches  glass 
easily),  infusibility,  insolubility,  non-action  of  acids,  and 
absence  of  cleavage,  are  the  characters  that  serve  to  distin- 
guish quartz  from  the  other  ingi'cdients  of  rocks. 

Although  quartz  is  one  of  the  original  minerals  of  tho 
earth's  crust,  the  quartz  of  rocks  is  not  all  directly  of  mine- 
ral origin.  Part  of  it — perhaps  a  large  part — has  passed 
through  living  beings,  either  plants 'or  animals;  for  some 


CONSTITUENTS   OP   ROCKS.  15 

of  the  lowest  species  of  these  kingdoms  of  life  have  the 
power  of  making  siliceous  shells  or  forming  siliceous  par- 
ticles or  spicules  in  their  texture;  and  beds  have  been  made 
of  these  microscopic  siliceous  shells.  The  animal  species 
that  secrete  spicules  of  silica  are  the  Sponges;  and  those 
making  siliceous  shells  are  the  microscopic  forms  called 
Polycystines.  The  plants  making  siliceous  shells  are  the 
microscopic  kinds  called  Diatoms.  (See  page  61.) 

2.  Silicates. — Silica  also  occurs  in  many  of  the  other  rock- 
making  minerals,  constituting  what  are  called  silicates.  It 
exists,  thus,  in  combination  with  the  bases  alumina,  mag- 
nesia, lime,  potash,  soda,  the  oxyds  of  iron,  and  a  few 
others. 

Pure  alumina,  the  most  important  of  the  above-mentioned 
bases  in  the  silicates,  is  hard,  infusible,  and  insoluble,  and 
therefore  adapted  to  be  next  in  abundance  to  silica.  When 
ciystallized,  it  is  the  hardest  of  all  known  substances,  ex- 
cepting the  diamond,  it  being  the  gem  sapphire.  A  massive 
or  rock-like  variety,  reduced  to  powder,  is  emery. 

Magnesia,  well  known  under  the  form  of  calcined  mag- 
nesia, is  as  hard  as  quartz  when  crystallized,  and  equally 
infusible  and  insoluble. 

Lime  is  common  quick-lime.  Potash  and  soda  are  the 
alkalies  ordinarily  so  called.  These  three  ingredients  are 
found  in  those  silicates  that  contain  also  either  alumina  or 
magnesia,  or  both.  The  same  is  true,  for  the  most  part,  of 
the  oxyds  of  iron.  The  compounds  they  form  have  a  degree 
of  fusibility  that  docs  not  belong  to  the  simple  alumina- 
silicates,  and  which  fits  them  for  being  the  constituents  of 
igneous  or  volcanic  rocks.  The  following  are  the  most 
common  of  these  silicates: — 

(1.)  Feldspar. — Feldspar  consists  of  silica  and  alumina 
along  with  lime,  potash,  or  soda.  Common  feldspar,  or  ortho- 
dose,  contains  mainly  potash,  along  with  the  silica  and  alu- 
mina; albite  contains,  in  place  of  the  potash,  soda;  and 


itj  LITHOLOGICAL   GEOLOGY. 

labradorite,  another  kind  of  feldspar,  contains  mainly  lime. 
The  specific  gravity  is  2.4-2.7. 

Either  of  these  kinds  of  feldspar  is  distinguished  from 
quartz  by  having  a  distinct  cleavage-structure,  the  grains 
or  masses  breaking  easily  in  two  directions  with  a  flat  and 
shining  surface.  They  are  nearly  as  hard  as  quartz,  often 
white,  but  sometimes  flesh-red.  The  albite  is  usually  white; 
and  the  labradorite  often  brownish,  with  generally  a  beau- 
tiful play  of  colors. 

(2.)  jlfica. — Mica  consists  of  silica  and  alumina,  along  with 
potash,  lime,  magnesia,  or  oxyd  of  iron.  It  cleaves  easily 
into  tough  leaves,  thinner  than  the  thinnest  paper  and 
somewhat  clastic.  On  account  of  its  transparency,  when 
colorless,  it  is  often  used  in  the  doors  of  stoves.  Its  most 
common  colors  are  whitish,  brownish,  and  black. 

The  minerals  quartz,  feldspar,  and  mica  are  the  con- 
stituents of  granite ;  and  they  may  be  distinguished  in  it 
as  follows :  the  quartz  by  its  more  glassy  lustre  and  want 
of  cleavage;  the  feldspar  by  its  being  more  opaque  than 
quartz,  and  its  having  cleavage;  the  mica  by  its  very  easy 
cleavage  into  thin,  elastic  leaves. 

(3.)  Hornblende  and  pyroxene. — Hornblende  and  pyroxene 
consist,  alike,  of  silica  along  with  magnesia,  lime,  and  prot- 
oxyd  of  iron.  They  are  both  of  dark-green,  greenish-black, 
and  black  colors  in  most  of  the  rocks  formed  of  them, 
though  sometimes  gray  and  white.  Both  are  cleavable. 
Hornblende  often  occurs  in  slender  needle-shaped  crystals. 
There  are  fibrous  varieties  of  each,  called  asbestus.  They  are 
nearlj"  as  hard  as  feldspar,  but  much  heavier  than  it  (spe- 
cific gravity  =  3-3.5),  and  in  general  much  more  fusible. 

(4.)  Garnet — Tourmaline — Andalusite. — These  are  other 
silicates,  of  very  common  occurrence  in  rocks.  They  are 
usually  found  in  crystals  distributed  through  a  rock.  Gar- 
net is  commonly  in  dark  red,  brownish,  or  black  crystals 
of  12  or  24  sides  (dodecahedrons  or  trapezohedrons).  Tho 


CONSTITUENTS   OF   ROCKS. 


17 


first  of  these  forms  is  represented  in  fig.  5,  showing  garnets 
distributed  through  a  mica  schist.     Tourmaline  is  generally 


Fig.  7. 


in  oblong  3,  6,  9,  or  12  sided  crystals,  shining  and  black; 
also  at  times  blue-black,  brown,  green,  and  red.  The  crys- 
tals are  common  in  gneiss  and  mica  schist,  and  are  at  times 
imbedded  in  quartz  (fig.  6).  Andalusite  is  found  in  imbedded 
crystals  in  argillaceous  schist :  the  form  is  nearly  a  square 
prism.  The  interior  of  the 
crystals  is  very  frequently 
black  or  grayish-black  at  the 
centre  and  angles  (fig.  7),  while 
the  rest  is  nearly  white;  and 
this  variety  is  called  made,  or 
chiastolite. 

(5 )  Talc  and  serpentine. — 
Talc  and  serpentine  are  com- 
pounds of  silica  with  magnesia 
and  water.  They  both  have  a  greasy  feel, — especially  the  talc. 
Talc  is  a  very  soft  mineral.  It  is  often  in  foliated  plates  or 
masses  like  mica;  but  the  folia,  or  leaves,  though  separating 
rather  easily  and  flexible,  are  not  elastic.  The  usual  color 
is  pale  green. 

A  massive  granular  talc,  of  whitish,  grayish,  or  greenish 
color,  is  called  soapstone,  or  steatite.  Serpentine  is  harder 
than  talc.  It  occurs  as  a  dark-green  massive  rock,  of  a  very 


18  LITHOLOGICAL    GEOLOG5T. 

fine-grained  texture :  it  is  rarely  foliated,  and  when  so,  the 
leaves  are  not  easily  separated  and  are  brittle.  It  may  be 
carved  with  a  knife,  and  it  differs  in  this,  and  also  in  its  being 
lighter,  from  compact  hornblendic  rocks. 

3.  Carbon,  Carbonic  Acid,  Carbonates. — (1.)  Carbon. — Car- 
bon is  familiarly  known  nnder  three  names  and  conditions  : 
(1.)  Diamond;  (2.)  Charcoal;  (3.)  Graphite.  The  last  is  the 
material  of  lead-pencils,  and  is  called  also  black  lead,  though 
containing  no  lead.  The  first  is  the  hardest  of  all  known 
substances;  the  last,  one  of  the  softest. 

In  Geology,  carbon  is  most  important  in  the  state  of 
mineral  coal,  which  is  carbon  mixed  with  other  ingredients, 
especially  some  of  a  bituminous  kind.  The  variety  con- 
taining bitumen  or  bituminous  substances  burns  on  this 
account  with  a  bright  flame,  and  is  called  bituminous  coal. 
The  harder  kind,  with  little  or  no  bitumen,  burning  with  a 
very  feeble-bluish  or  yellowish  flame,  is  anthracite.  Lignite 
is  a  coal  retaining  in  part  the  structure  of  the  original 
wood,  and  having  an  empyreumatic  odor  when  burned. 

(2.)  Carbonic  acid  is  a  gas  consisting  of  carbon  and  oxygen. 
It  composes  about  4  parts  by  volume  of  10,000  parts  of 
the  atmosr>here,  is  formed  in  all  combustion  of  wood  or  coal, 
and  is  given  out  in  the  respiration  of  animals. 

(3.)  Carbonate  of  lime,  or  calcite,  the  essential  ingredient 
of  limestone  and  marble,  consists  of  carbonic  acid  and  lime. 
It  crystallizes  in  a  great  variety  of  forms,  a  few  of  which 
are  represented  in  figs.  8,  9.  It  cleaves  easily  in  three  direc- 
tions with  bright  surfaces ;  as  may  be  seen  on  examining  even 
the  grains  of  a  fine  white  marble.  It  is  rather  soft,  so  as  to 
be  easily  scratched  with  a  knife ;  dissolves  in  diluted  acids 
(chlorohydric  or  sulphuric)  with  effervescence,  that  is,  with 
an  escape  of  the  gas  carbonic  acid ;  and  when  heated  (as  in  a 
lime-kiln,  or  before  the  blowpipe)  it  burns  to  quick-lime  with- 
out melting.  By  its  effervescence  with  acids  it  differs  from 
all  the  minerals  before  mentioned. 


CONSTITUENTS    OF   ROCKS. 


Fig.  8. 


Fig.  9. 


(4.)  Dolomite  is  a  carbonate  of  lime  and  magnesia;  that  ia, 
it  differs  from  calcite  in  containing  magnesia  in  place  of 
part  of  the  lime.  It  makes  up  the  mass  of  a  Variety  of 
limestone  called  magnesian  limestone,  which  closely  resem- 
bles common  limestone,  but  may  be  distinguished  by  ita 
effervescing  scarcely  at  all  with  acid  unless  heat  be  applied. 
The  trial  may  be  made  by  dropping  a  particle,  as  large  as 
half  a  grain  of  wheat,  into  a  test-glass  one-quarter  filled 
with  a  mixture,  half  and  half,  of  muriatic  acid  and  water. 

The  larger  part  of  the  carbonate  of  lime  of  rocks  has  been 
derived  directly  from  shells,  corals,  and  other  animal  re- 
mains. Animals  take  the  material  of  their  shells  and  other 
stony  structures  from  the  waters  of  the  globe,  or  from  the 
food  they  eat,  through  their  power  of  secretion, — that  is, 
the  same  power  by  which  man  forms  his  bones.  After 
death,  the  shells,  corals,  or  bones,  which  are  of  no  further 
use  to  the  species,  are  turned  over  to  the  mineral  kingdom 
to  be  made  into  rocks.  The  immense  extent  and  thickness 
of  the  earth's  limestone  rocks,  nearly  all  of  which  are  proba- 
bly of  organic  origin,  give  some  idea  of  the  amount  of  life 
that  has  lived  and  died  through  past  time. 

Carbonate  of  lime  and  silica  are  the  two  stony  ingre- 
dients which  have  been  contributed  largely  by  living 
species  to  the  earth's  rock-formations.  Mineral  coal  is  an- 

3 


20  UTHOLOGICAL    GEOLOGY. 

other  material  abundantly  contributed  by  the  kingdoms  of 
life,  the  great  beds  of  the  coal  period  being  all  made  from 
the  leaves  and  other  parts  of  plants. 

Sand — Clay. — Sand  and  clay  are  not  minerals  :  they  are 
mixtures  of  minute  particles  of  different  minerals,  produced 
by  the  wearing  down  of  different  rocks.  A  large  part  of 
common  clay  is  pulverized  feldspar  mixed  with  some  quartz. 
Other  kinds,  having  a  greasy  feel  in  the  fingers,  consist  of 
a  material  derived  from  the  decomposition  of  feldspar  and 
allied  minerals,  and  are  composed  of  alumina,  silica,  and 
water,  mixed  more  or  less  with  quartz  and  other  impurities. 

2.  KINDS  or  EOCKS. 

1.  Fragmental  and  Crystalline  rocks. — The  minerals  of  which 
a  rock  consists  may  be  either  (1)  in  broken  or  worn  grains 
or  pebbles,  like  those  of  sand  or  clay  or  a  bed  of  pebbles ;  or 
^'3)  they  may  be  in  crystalline  grains,  in  which  case  they 
\vere  formed  where  they  now  are  at  the  time  of  the  crys- 
tallization of  the  rock.  Such  crystalline  grains  are  angular, 
and  almost  always  show  surfaces  of  cleavage. 

The  rocks  of  the  first  kind,  consisting  of  a  mingling  of 
fragments  of  other  rocks,  are  called  fragmented  rocks ;  and 
those  of  the  latter  kind,  crystalline  rocks.  The  sands  of  a  sea- 
shore or  the  mud  of  a  sea-bottom  may  make  a  fragmental 
rock  no  less  than  coarser  deposits. 

Fragmental  rocks  are  often  called,  also,  sedimentary  rocks, 
because  formed  in  general  from  sediment,  or  the  earth  depo- 
sited by  waters,  either  those  of  the  ocean,  lakes,  or  rivers. 

Intermediate  between  rocks  that  are  obviously  either  frag- 
mental or  crystalline,  there  are  others,  of  a  flinty  compactness, 
which  show  no  distinct  grains,  and  are,  therefore,  not  easily 
referred  to  either  division.  In  the  case  of  such  rocks,  the 
geologist,  in  order  to  determine  the  division  to  which  they 
belong,  has  to  examine  the  rocks  associated  with  them.  If 
these  associated  rocks  are  fragmental,  then  the  co'npact  beds 


KINDS   OF   ROCKS.  21 

are  probably  so  also ;  but  if  these  are  crystalline,  then  they 
are  probably  related  to  the  crystalline.  Experience  among 
rocks  is  required  to  decide  correctly  in  all  such  cases. 

2.  Metamorphic  and  Igneous  rocks. — The  crystalline  rocks 
are  either  metamorphic,  or  igneous. 

1.  Metamorphic  rocks  are  those  which  have  been  altered 
or  metamorphosed  by  means  of  heat.     The  alteration,  when 
most  complete,  consists  in  a  complete  crystallization  of  the 
rock ;  and  when  less  so,  in  a  consolidation  or  baking  of  it, 
with  sometimes  no  distinct  crystallization. 

Earthy  sandstones  and  clay-rocks  have  been  thus  meta- 
morphosed into  granite,  gneiss,  and  mica  schist,  and  ordinary 
limestone  into  statuary  marble, 

2.  Igneous  rocks  are  those  which  have  been  ejected  in  a 
melted  state,  as  from  volcanic  vents,  or  from  fissures  opened 
to  some  seat  of  fires  below  or  within  the  earth's  crust. 

3.  Calcareous  rocks. — Calcareous  rocks  are  the  limestones. 
To  a  great  extent  they  have  been  formed  from  pulverized 
animal  relics,  such  as  shells  and  corals ;  and  in  this  case  they 
are  properly  fragmental  or  sedimentary  beds,  although  so 
finely  compact  that  this  might  not  be  suspected  from  their 
texture. 

Some  limestones  have  been  made  from  the  accumulation 
and  consolidation  of  very  minute  shells,  called  Ehizopods. 
These  shells  being  no  larger  than  the  finest  grains  of  sand, 
no  powdering  was  necessary.  The  limestone  rocks  formed 
of  them  are  not  fragmental  in  origin. 

Other  calcareous  rocks  have  been  deposited  from  waters 
holding  the  material  in  solution,  and  are,  therefore,  of  chemi- 
cal origin.  Of  this  kind  is  the  travertine  of  Tivoli  near 
Rome  in  Italy,  and  similar  beds  in  many  regions  of  mineral 
springs,  besides  the  petrified  moss  and  trees  of  some  marshy 
regions. 

4.  Massive,  schistose,  laminated,  slaty,  shaly  rocks. — Rocks 
are  termed  massive,  when  there  is  no  tendency  to  break  ink/ 


22  LITHOLOGICAL    GEOLOGY. 

slabs  or  plates;  schistose,  when  crystalline  and  having  a  tend- 
ency to  break,  into  slabs  or  plates,  arising  from  the  arrange- 
ment more  or  less  perfectly  in  layers  of  the  mineral  ingre- 
dients (especially  mica  or  hornblende) ;  laminated,  when 
breaking  into  slabs  or  flagging-stones,  and  not  in  conse- 
quence of  a  crystalline  structure;  slaty,  when  dividing  easily 
into  thin,  even,  hard  slates,  like  roofing-slate;  shaly,  when 
dividing  easily  into  thin  plates  like  a  slate-rock,  but  the 
plates  irregular  and  fragile. 

The  term  schist  is  applied  to  a  schistose  rock;  flag,  to 
a  laminated  rock;  slate,  to  a  slaty  rock;  shale,  to  a  shaly 
rock. 

The  kinds  of  rocks  may  be  described  under  the  four  heads : — 
(1)  Fragmental rocks,  not  calcareous;  (2)  Metamorphic  rocks, 
not  calcareous;  (3)  Calcareous  rocks;  (4)  Igneous  rocks. 

1.  Fragmental  Rocks. 

1.  Sandstone. — Composed  of  sand,  coarse  or  fine.     "When 
of  pure  quartz  sand,  the  rock  is  a  siliceous  sandstone;  and  if 
very  hard   and  a  little   pebbly,  a  grit.     When   earthy  or 
clayey,  it  is  an  argillaceous  sandstone,  the  term  argillaceous 
meaning  clayey.     Argillaceous  sandstones  are  usually  lami- 
nated, and,  when  very  hard,  may  make  good  flagging-stone. 

2.  Conglomerate. — Containing  rounded  or  angular  pebbles. 
If  rounded  pebbles,  the  rock  is  often  called  a  pudding-stone; 
and  if  angular  fragments,  a  breccia;  if  the  pebbles  are  of 
quartz,  a  siliceous  conglomerate;  if  of  limestone,  a  calcareous 
conglomerate. 

3.  Shale. — Composed  of  clay  or  clayey  earth,  and  having 
a  shaly  structure.     The  colors  are  of  all  dull  shades  from 
gray  to  black.     When  the  shaly  structure  is  very  imperfect 
and  the  rock  is  quite  fragile,  it  is  a  marlite.     [It  is  often 
called,  though  not  correctly;  a  marl:  a  true  marl  is  a  clay 
containing  carbonate  of  lime  derived  generally  from  pow- 
dered or  broken  shells.] 


KINDS    OF   ROCKS.  28 

4.  Tufa. — A  kind  of  volcanic  sandstone,  composed  of  vol- 
canic sand  or  pulverized  volcanic  rocks :  color,  usually 
brownish,  brownish-yellow,  grayish,  and  reddish. 

2.  Metamorphic  Rocks. 

1.  Granite. — A  crystalline  rock,  consisting  of  quartz,  feld- 
spar, and  mica.    Color.,  usually  light  or  dark  gray  or  flesh- 
red,  the  latter  shade  derived  from  a  flesh-colored  feldspar. 

2.  Gneiss. — Closely  like  granite  in  composition,  but  some- 
what schistose,  and,  consequently,  having  a  banded  appear- 
ance on  a  surface  of  fracture  transverse  to  the  structure, 
arising  from  the  arrangement  of  the  mica.     If  the  color  of 
the  gneiss  is  dark  gray,  it  is  banded  usually  with  black 
lines.     Along  the  micaceous  planes  it  breaks  rather  easily 
into  slabs,  which  are  sometimes  used  for  flagging. 

3.  Mica  Schist. — Eelated  to  gneiss,  but  consisting  mainly 
of  mica,  with  more  or  less  of  feldspar  and  quartz,  and,  in 
consequence  of  the  mica,  breaking  into  thin  slabs.      The 
slabs  have  a  glistening  surface.     In  regions  of  mica  schist 
the  dust  of  the  roads  is  often  full  of  shining  particles  of  mica. 

4.  Syenite — Hornblendic  Gneiss — Hornblendic  Schist. — Syen- 
ite resembles  granite,  but  contains  hornblende  in  place  of 
mica :  the  hornblende  may  be  distinguished  from  mica  by 
its   less   perfect   cleavage,  and   by   the   brittleness   of  the 
lamina  afforded  with  some  difficulty  by  the  cleavage.     A 
rock  like  gneiss,  but  containing  hornblende  in  place  of  mica, 
is   called   hornblendic    gneiss.      A   black    or   greenish-black 
schistose  rock  consisting   almost  wholly  of  hornblende  is 
called  hornblendic  schist. 

5.  Talcose  Schist. — A  slaty  rock  containing  some  talc,  and 
having,    therefore,   a    greasy  feel.     Color  usually  grayish- 
green,  greenish,  or  brownish. 

G.  Chlorite  Schist. — A  slaty  rock  containing  an  olive- 
green  mineral  called  chlorite,  waish.  is  related  to  talc  in 


24  LITHOLOaiCAL   GEOLOGY. 

being  magncsian,  but  contains  oxyd  of  iron,  and  is  hardly 
greasy  in  feel      Color,  dark  green,  and  often  olive  green. 

7.  Slate,  Argillite,  Argillaceous  Schist. — These  arc  different 
names  of  roofing-slate  and  the  allied  slaty  rocks.     The  tex- 
ture is  hardly  at  all  crystalline,  but  the  slates  in  the  most 
perfect  kinds  are  hard,  smooth  in  surface,  and  not  absorbent 
of  water.      Color    blue-black,   purplish,    greenish,   and   of 
other  shades. 

There  is  a  gradual  passage  of  the  above  rocks  from  gra- 
nite into  gneiss ;  from  gneiss  into  mica  schist ;  and  from 
mica  schist  and  talcose  schist  into  argillaceous  schist. 

8.  Quartz  Rock — Quartzite. — There  is  also  a  gradual  pass- 
age, through  the  more  or  less  complete  absence  of  the  feld- 
spar,,into  a  micaceous  quartz  rock  having  a  schistose  struc- 
ture; and,  by  a  more  or  less  complete  absence  of  the  mica 
into    a    pure    massive    quartz    rock,    called    also    quartzite. 
Quartzite  is  only  a  very  firmly  consolidated  sandstone  made 
of  quartz  sand.     The  consolidation  has  been  produced  by 
the  aid  of  heat,  just  as  crystallization  into 'gneiss  has  been 
produced.     For  the  former  the  sandstones  -were  purely  sili- 
ceous, or  nearly  so,  and  for  the  latter,  earthy  sandstones. 

9.  Itacolumite. — A  peculiar  laminated  quartz  rock  occurs 
in    many    gold-regions,   which    bends    without    breaking, 
when  in  large  thin  plates.    It  contains  scales  of  mica  or 
talc,  and  owes  to  this  its  laminated  structure,  toughness, 
and  flexibility. 

3.  Calcareous  Hocks. 

a.    Uncrystalline. 

1.  Common  Limestone. — A  compact  rock,  of  grayish  and 
other  dull  shades  of  color  to  black,  breaking  with  little  or 
no  lustre,  and  with  either  a  slightly  rough  or  a  smooth  sur- 
face of  fracture.  Consists  essentially  of  carbonate  of  lime, 
though  often  very  impure  from  the  presence  of  clay  or  earth. 
When  containing  fossils,  it  is  called  fossiliferous  limestone. 


KINDS   OF   ROCKS.  25 

When  consisting  of  carbonate  of  lime  and  magnesia,  it  is  a 
magnesian  or  dolomitic  limestone,  or  dolomite,  a  kind  not  dis- 
tinguishable  by  the  eye  from  ordinary  limestone.  For  the 
distinctive  characters,  see  page  17. 

Many  varieties  of  common  limestone  are  polished  and 
used  as  marbles.  The  black  marbles,  and  some  of  the  yellow 
and  gray,  are  of  this  kind.  Frequently  they  contain  fossils. 

2.  Oolite. — A  limestone  consisting  of  concretions  as  small 
as  the  roe  offish, — whence  the  name,  from  the  Greek  oon,  egg. 
Oolites  or  oolitic  limestones    occur  in  all   the  geological 
formations,  and  are  forming  in  modern  seas  about  some 
coral  reefs. 

3.  Travertine. — See  page  21. — Stalactites  are  limestone  con- 
cretions, of  the  form  of  icicles,  hanging  from  the  roofs  of 
caverns ;  and  Stalagmite  is  the  same  material  covering  their 
floors.     The  waters  trickling  through  limestone  rocks  hold 
some  carbonate  of  lime  in  solution  (in  the  state  of  bicar- 
bonate) ;  and  its  deposition,  as  the  dropping  water  evapor- 
ates, produces  these  concretions  and  incrustations. 

b.  Crystalline. 

Granular  Limestone — Statuary  Marble. — Limestone  having 
a  crystalline  granular  texture,  and,  consequently,  glistening 
on  a  surface  of  fracture.  The  pure  white  kind,  looking 
when  broken  much  like  loaf-sugar,  is,  when  of  firm  texture, 
the  marble  used  for  statuary;  and  both  this  and  coarser 
varieties  are  employed  for  marble  buildings.  Most  of  the 
clouded  marbles  are  here  included. 

4.  Igneous  Rocks. 

1.  Granite-like  Rocks. — Granite  is  usually  regarded  as  a 
true  igneous  rock.  But  igneous  rocks  contain  ordinarily 
little  or  no  silica  in  the  condition  of  quartz.  There  are 
several  kinds  of  whitish  and  grayish  crystalline  igneous 
rocks  consisting  of  feldspar  and  hornblende,  or  feldspar  and 


26  LITHOLOGICAL   GEOLOGY. 

pyroxene,  or  feldspar  alone,  each  containing  little  or  no 
quartz.     Mica  is  sometimes  present  in  rocks  of  this  kind. 

2.  Diorite. — Consists  of  a  feldspar  (albite)  and  hornblende; 
and,  though  it  may  be  light-colored  from  the  abundance  of 
the  feldspar,  it  is  usually  dark  green  and  greenish-black, 
from  the  preponderance  of  the  hornblende. 

3.  Dolerite. — Consists   of   a    feldspar    (labradorite)    and 
pyroxene,    and    has    greenish-black,    brownish-black,    and 
black  colors.     It  is  also  often  called  trap.     It  may  be  either 
crystalline   granular,  or  of  a    flinty  compactness.     It  fre- 
quently contains  also  grains  of  magnetic  iron  ore. 

4.  Basalt. — Like  dolerite,  but  containing  grains  of  a  green 
siliceous  mineral,  of  a  bottle-glass  green  color,  called  chryso- 
lite or  olivine. 

5.  Trap. — Basalt,  dolerite,  and  the  diorites,  especially  the 
dark-colored  kinds,  are  often  called  trap,  or  trappean  rocks. 

6.  Porphyry. — Consists  of  feldspar  (orthoclase)  in  a  com- 
pact condition,  and  contains  crystals  of  feldspar  of  a  paler 
color  and  often  whitish ;  so  that  a  polished  surface  is  covered 
with  angular  spots.     Common  colors,  green  and  red. 

Granite,  dolerite,  basalt,  and  other  rocks  are  said  to  be 
porphyritic  when  the  feldspar  is  in  distinct  crystals. 

A  large  part  of  the  so-called  porphyry  is  of  metamorphic 
origin,  and  not  a  true  igneous  rock.  It  sometimes  consists 
in  part  of  hornblende  or  quartz. 

7.  Trachyte. — Consists  of  feldspar,  and  has  a  rough  surface 
of  fracture.     Usually  contains  small  air-cells,  and  also  dis- 
seminated crystals  of  a  glassy  feldspar. 

8.  Lava. — Any  rock  that  has  flowed  in  streams  from  a 
volcano,  especially  if  it  contains  cavities,  or,  in  other  words,  is 
more  or  less  scoriaceous.     It  is  usually  a  dolerite,  basalt,  or 
trachyte  in  composition. 

9.  Scoria  is  a  light  lava,  full  of  cavities,  like  a  sponge;  and 
-pumice,  a  white  or  grayish  feldspathic  scoria,  having  the  air- 
cells  long  and  slender,  so  that  it  looks  as  if  it  were  fibrous. 


STRATIFIED   ROCKS.  27 


2.  CONDITION,  STRUCTURE,  AND  ARRANGEMENT  OF  ROCK- 
MASSES. 

The  rocks  which  have  been  described  are  the  common 
material  of  which  the  great  rock-masses  of  the  globe  consist. 
These  rock-masses  occur  under  three  conditions : — (1)  the 
stratified ;  (2)  the  unstratified;  (3)  the  vein-form. 

1.  The  Stratified  condition. — Stratified  rocks  are  those 
which  ho  in  beds  or  strata.  The  word  stratum  (the  singular 
of  strata)  is  from  the  Latin,  and  signifies  that  which  is 
spread  out.  The  earth's  rocky  strata  are  spread  out  in  beds 
of  vast  extent,  many  of  them  covering  thousands  of  square 
miles.  The  stratified  rocks  exposed  to  view  over  the  earth's 
surface  far  exceed  in  area  the  unstratified. 

They  are  the  rocks  of  nearly  the  whole  of  the  United 
States  and  of  nearly  all  of  North  America,  and  not  less  of 
the  other  continents.  Throughout  central  and  western  New 
York  and  the  States  south  and  west,  the  rocks,  wherever  ex- 
posed, are  seen  to  be  made  up  of  a  series  of  beds.  And  if  the 
beds  are  less  distinct  over  a  large  part  of  New  England,  it 
is,  in  general,  only  because  they  have  been  obscured  by  the 
upturning  and  crystallization  which  the  rocks  have  under- 
gone since  they  were  formed. 

Fig.  10. 


The  preceding  figure  represents  a  section  of  the  rocks 
along  the  river  below  Niagara  Falls.  It  gives  some  idea  of 
the  alternations  which  occur  in  the  strata.  In  a  total  height 
of  250  feet  (165  feet  at  the  Falls,  at  F,  on  the  right)  there 


28  .  LITHOLOGICAL   GEOLOGY. 

are  on  the  left  6  different  strata  in  view  and  parts  of  2 
others,  the  upper  and  lower,  making  8  in  all.  1  is  gray 
argillaceous  sandstone;  2,  gray  and  red  argillaceous  sand- 
stone and  shale;  3,  flagstone,  or  hard  laminated  sandstone; 
4,  reddish  shale  or  marlite  and  shaly  sandstone ;  5,  shale ;  6, 
limestone;  7,  shale;  8,  limestone.  Only  two  of  these  strata, 
7  and  8,  are  in  sight  at  the  falls  (at  F).  The  alternations 
are  thus  numerous  and  various  in  all  regions  of  stratified 
rocks. 

It  must  not  be  inferred  that  the  earth  is  covered  by  a 
regular  series  of  coats,  the  same  in  all  countries ;  for  this  is 
far  from  the  truth.  Many  strata  occur  in  New  York  that 
are  not  found  in  Ohio  and  the  States  west ;  and  each  stratum 
varies  greatly  in  different  regions,  sometimes  being  lime- 
stone in  one  and  sandstone  in  another. 

A  stratum  is  a  bed  of  rock  including  all  of  any  one  kind 
that  lie  together,  as  either  Nos.  1,  2,  3,  4,  5,  6,  7,  or  8  in  the 
preceding  figure. 

A  formation  includes  the  several  strata  that  were  formed  in 
one  age  or  period.  A  subdivision  of  a  formation,  including 
two  or  more  related  strata,  is  often  called  a  group. 

A  layer  is  one  of  the  subdivisions  of  a  stratum.  A  stratum 
may  consist  of  an  indefinite  number  of  layers. 

2.  TJnstratified  condition. — Unstratified  rocks  are  those 
which  do  not  lie  in  beds  or  strata.  Mountain-masses  of 
granite  are  often  without  any  appearance  of  stratification. 
The  rock  of  the  Palisades,  on  the  Hudson,  stands  up  with  a 
bold  columnar  front,  and  has  no  division  into  layers.  There 
are  similar  rocks  about  Lake  Superior.  Most  lavas  of  vol- 
canoes have  flowed  out  in  successive  streams;  and,  conse- 
quently, volcanic  mountains  are  generally  stratified.  Bat  in 
some  volcanic  regions  the  rocks  rise  into  lofty  summits 
vrithout  stratification.  Although  true  granite  bears  no 
marks  of  proper  stratification,  it  very  often  passes  insensibly 
into  gneiss,  which  is  a  Ptratified  rock;  and  there  is  evi- 


VEINS. 


29 


dence  in  this  fact  that  granite  is,  generally,  a  stratified  rock 
which  has  lost  the  appearance  of  stratification  in  consequence 
of  the  crystallization  it  has  undergone. 

3.  Vein-form  condition. — When  rocks  have  been  fractured, 
and  the  fissures  thus  made  have  been  filled  with  rock-mate- 
rial of  any  kind,  or  with  metallic  ores,  the  fillings  are  called 
veins.  Veins  are  therefore  large  or  small, — deep  or  shallow, 
— single  or  like  a  complete  network, — according  to  the  cha- 
racter of  the  fractures  in  which  they  were  formed.  They 


Fig.  11. 


Fig.  12. 


may  be  as  thin  as  paper,  or  they  may  be  many  yards,  or 
even  rods,  in  width.  Figures  11  to  14  represent  some  of 
them.  In  fig.  11  there  are  two  veins,  a  and  b ;  in  fig.  12, 


Fig.  13. 


Fig.  14. 


a  network  of  thin  veins;  in  fig.  13,  two  of  irregular  form, — a 
kind  not  uncommon ;  in  fig.  14,  two  large  veins,  of  still  more 
irregular  character,  crossing  one  another. 


LITHOLOGICAL    GEOLOGY. 


Fig.  15. 
6  5   4321  2456 


Many  veins  have  a  banded  structure,  like  fig.  15.     In 
this  vein,  the  layers  1,  3,  6,  consisted  of  quartz;  2,  4,  of 
gneissoid    granite;    5,    of    gneiss.     Most 
metallic  veins  are  of  this  kind :  the  ores 
lie   in    one    or   more    bands    alternating 
with    other    stony    bands    consisting    of 
different    minerals    or  rock-material,   as 
calcite,  quartz,  fluor-spar,  etc. 

Those  veins  that  have  been  filled  with 
melted  rocks  are  usually  called  dikes: 
they  are  not  banded,  and  have  regular 
walls;  and  the  rocks  are  igneous  rocks. 
They  are  often  transversely  columnar  in 
structure.  Fig.  16  represents  a  dike, 
and  shows  this  transverse  columnar  structure. 

4.  Relation  of  stratified  and  true  unstratified  rocks  and  veins 
in  the  earth's  crust. — The    relations   of   the    stratified   and 
unstratified  rocks   in  the  earth's   crust  will  be 
understood  after  considering  the  origin  of  the 
crust. 

The  crust  is  believed  to  be  the  cooled  exterior 
of  a  melted  globe.  After  the  first  crusting  over 
of  the  surface  of  the  sphere,  the  ocean  com- 
menced to  make  stratified  rocks  over  the  exte- 
rior, while  the  continued  cooling,  going  on  very 
slowly,  made  unstratified  rocks  below.  The  ocean  thus 
worked  over  and  covered  up  with  strata  nearly  all,  if  not 
all,  the  original  unstratified  crystalline  rocks.  Hence, 
true  unstratified  rocks — that  is,  those  which  were  unstra- 
tified in  their  first  formation — are  of  very  small  extent 
over  the  globe.  Even  ordinary  granite,  as  mentioned  on 
page  29,  is  not  generally  of  this  kind.  Veins  are  a  result  of 
fractures  of  the  crust;  and  they  too  are  of  very  limited 
distribution. 

Geology,  consequently,  has  for  its  study,  almost  solely 


Fig.  16. 


STRUCTURE   OF   ROCKS. 


31 


stratified  rocks.  Nearly  all  the  facts  in  geological  history 
are  derived  from  rocks  of  this  kind.  It  is,  therefore,  import- 
ant that  the  various  details  with  regard  to  their  structure 
and  arrangement  should  be  well  understood  by  the  student. 

STRATIFIED  CONDITION. 

1.  Structure. 

1.  Massive,  laminated,  and  shaly  structures. — The  massive, 
laminated,  and  shaly  structures  of  layers  have  been  ex- 
plained on  p.  21.  The  massive  is  represented  in  fig.  17  a; 

Fig.  17. 


•.-•;-/.-.. i 


the  laminated,  in  fig.  17  b  ;  and  the  shaly,  in  fig.  17  c.  Sand- 
stone is  more  or  less  laminated,  according  to  the  proportion 
of  clay  or  earthy  material  it  contains.  The  same  is  true  of 
limestone. 

2.  Beach-structure. — The  beach-structure  is  illustrated  in 
fig.  17  d.     The  layer,  instead  of  being  composed  of  evenly- 
laid  material,  consists  of  many  irregular  small  layers, — beds 
of  sand  and  others  of  pebbles,  of  small  extent,  being  variously 
mingled.     This  kind  of  layer  is  formed  along  sea-beaches, 
being  well  shown  wherever  a  sea-beach  is  cut  through,  so 
that  the  interior  is  open  to  view. 

3.  Ebb-and-flow  structure. — The  ebb-and-flow  structure  is 

4 


LITHOLOGICAL   GEOLOGY. 


illustrated  in  fig.  17  e.  A  layer  presenting  it  consists  of 
irregular  subordinate  layers,  like  those  of  beach  origin ;  but 
these  subordinate  layers  are  of  wider  extent,  and  part  of 
them  are  obliquely  laminated  (see  figure,)  while  other  alter- 
nate layers  are  laminated  horizontally.  Such  a  structure  is 
formed  where  currents  intermit  at  intervals  or  are  reversed, 
as  in  the  ebb  and  flow  of  the  tides  where  they  are  connected 
with  heavy  tidal  waves. 

4.  Wind-drift  structure. — A  layer  characterized  by  the 
wind-drift  structure  consists  of  layers  dipping  in  various 
directions,  sometimes  curving  and  sometimes  straight.  (Fig. 
17  /.)  The  hills  of  sand  formed  by  the  winds  on  a  sea-coast 
usually  have  this  structure.  The  sands  drifted  over  the 
rising  heaps  form  layers  conforming  to  the  outer  surface, 
and  so  may  slope  at  all  angles.  In  storms  they  may  be 
blown  away  in  part,  and  afterwards  be  completed  again; 
but  then  the  layers,  conforming  to  a  new  outer  surface, 
would  have  a  different  direction.  In  this  way,  by  successive 


Fig.  18. 


Fig.  19. 


destructions  and  re-completions,  a  bed  of  sand  may  be  made 
which  shall  consist  of  parts  sloping  in  one  direction  and 


STRUCTURE    OF    ROCKS. 


33 


other  parts    in   directions  very  different,  with    numerous 
abrupt  transitions,  as  illustrated  in  the  drawing. 

5.  Hippie-marks. — A  gentle  flow  of  water  or  its  vibration, 
over  mud  or  sand,  ripples  the  surface.    Sandstone  and  clayey 
rocks  are  often  covered  with  such  ripple-marks.  (Fig.  18.) 

6.  Rill-marks. — When  the  waters  of  a  spreading  or  return- 
ing wave  on  a  beach  pass  by  shells  or  stones  lodged  in  the 
sand,  tb.3  rills  furrow  out  little  channels.     Fig.  19  shows 
such  rill-marks  alongside  of  shells  in  a  Silurian  sandstone. 

7.  Mud-cracks. — When  a  mud-flat  is  exposed  to  the  air  or 
sun  to  dry,  it  becomes  cracked  to  a  few  inches  or  so  in 
depth.      Fig.  20  represents  mud-cracks  in  an  argillaceous 
sandstone.    The  cracks  were  subsequently  filled  with  stony 
material,  which  was  harder  even  than  the  rock  itself;  so 
that  the  filling  stands  prominent  above  the  general  surface, 
and  is  actually  a  network  of  veins. 


Fig.  20. 


Fig.  21. 


8.  Rain-prints. — The  impressions  of  rain-drops  on  sand  or 
a  half-dry  mud   have  often  been  preserved  in  the  rocks, 
appearing  as  in  fig.  21. 
v-  9.   Concretionary  structure. — Layers  often  contain  spheres 


34 


LITHOLOGICAL   GEOLOGY. 


Fig.  22. 


or  disks  of  rock,  which  are  called  concretions.  They  result 
from  a  tendency  in  matter  to  concrete  or  solidify  around 
centres.  Some  are  no  larger  than  grains  of 
sand  or  the  roe  of  fish,  as  in  oolitic  limestone 
(p.  25).  Others  are  as  large  as  peas  or  bullets, 
and  others  a  foot  or  more  in  diameter.  Fig. 
22  is  one  of  a  spherical  form.  Fig.  23  repre- 
sents a  rock  made  up  of  rounded  concretions. 
It  shows  also  that  they  have  sometimes 
(though  not  always)  a  concentric  structure.  In  fig.  24  the 
concretions  are  flattened.  ' 


Fig.  23. 


Fig.  24. 


Fig.  25. 


^^-•.^-^-T^-^"^; 


Concretions  are  usually  globular  in  sandstones,  lenticular 
in  laminated  sandstones,  and  flattened  disks  in  argillaceous 
rocks  or  shales.  All  these  kinds  are  shown  in  fig.  25.  The 
balls  are  sometimes  hollow,  and  the  disks  mere  rings.  Fre- 
quently the  concretions  have  a  shell  or  other  organic  object 


Fig.  26 


Fig.  27. 


Fig.  28. 


at  centre  (fig.  26).  They  are  often  cracked  through  the 
interior  (fig.  27),  the  outside  in  such  a  case  having  solidified 
while  the  inside  was  still  moist,  and  the  latter  afterwards 
cracking  as  it  dried :  in  such  a  case  the  cracks  may  become 


STRUCTURE    OF    ROCKS. 


35 


Tig.  29. 


filled  with  other  minerals,  so  that  the  concretion,  on  being 
sawn  in  two  and  polished,  may  have  great  beauty.  When 
hollow,  they  may  be  afterwards  incrusted  within  by  crys- 
tals (fig.  28)  as  of  quartz,  or  by  layers  as  of  agate,  and  thus 
make  what  is  called  a  geode ;  or  they  may  become  wholly 
filled.  Sometimes  they  contain  a  loose  ball  within, — a  con- 
cretion within  a  concretion. 

Basaltic  columns  (fig.  29),  as  they  are  often  called,  are  col- 
umns of  igneous  rock  made  by 
the  contraction  of  the  mass  when 
cooling  from  fusion.  The  size 
of  the  columns  depends  on  a 
concretionary  structure  forming 
at  the  time  within.  The  tops 
of  the  columns  are  often  con- 
cave, or  they  become  so  as  the 
rock  decomposes. 

10.    Jointed    structure.  —  The 

rocks  of  a  region  are  often  divided  very  regularly  by  nume- 
rous straight  planes  of  fracture,  all  parallel  to  one  another,  and 
cutting  through  to  great  depths.  Such  planes  of  fracture  may 
characterize  the  rocks  for  hundreds  of  miles.  They  are 

Fig.  30. 


catted  joints;  and  a  rock  thus  divided  is  said  to  present  &  jointed 
structure.  In  many  cases  there  are  two  systems  of  joints  in 
the  same  region,  crossing  one  another,  so  that  they  divide 


36  LITHOLOGICAL   GEOLOGY. 

the  rock  into  angular  blocks,  or  give  to  a  bluff  a  front  like 
that  of  a  fortification  or  a  broken  wall,  as  shown  in  fig.  30, 
— a  view  from  the  shores  of  Cayuga  Lake.  The  directions 
of  such  joints  are  facts  which  the  geologist  notes  down  with 
care. 

11.  Slaty  cleavage. — The  term  slaty  has  been  explained  on 
page '22.  But  one  important  fact  regarding  the  structure  is 
not  there  stated,  which  is,  that  the  slates  are  always  trans- 
verse to  the  bedding,  that  is,  they  cross  the  layers  of  stratifi- 
cation more  or  less  obliquely,  instead  of  conforming  to  the 
layers  like  the  shaly  structure.  Slaty  cleavage  is  in  this 
respect  like  the  jointed  structure;  but  it  differs  in  having 
the  planes  of  fracture  or  divisional  planes  so  close  and  nume- 
rous that  the  rock  divides  into,  slates  instead  of  blocks. 

Slaty  cleavage  is  confined  to  fine-grained  argillaceous 

Fig.  31.  Fig.  32. 


rocks.  If  a  rock  is  a  coarse  argillaceous  rock  or  an  argil- 
laceous sandstone,  it  may  have  a  jointed  structure,  but  will 
not  have  the  true  slaty  cleavage.  In  fig.  31  the  lines  of 
bedding  or  stratification  are  shown  at  a,  b,  c,  d,  while  the 
transverse  lines  correspond  to  the  direction  of  the  slates. 
The  same  is  shown  in  fig.  32,  with  the  addition  of  a  slight 
irregularity  in  the  slates  along  the  junction  of  two  layers. 

2.  Positions  of  Strata. 

1.  Original  position  of  strata. — Horizontal  position. — Ordi- 
nary stratified  rocks  were  once  beds  of  sand  or  earth,  or  of 
other  kinds  of  rock-material,  spread  out  for  the  most  part 
by  the  currents  and  waves  of  the  ocean,  but  partly  by  the 
waters  of  lakes  or  rivers. 


POSITIONS   OF    STRATA.  37 

"When  the  larger  portion  of  the  beds  over  the  North  Ame- 
rican continent  were  formed,  the  continent  lay  to  a  great 
extent  beneath  the  ocean,  as  the  bottom  of  a  great,  though 
shallow,  continental  sea.  The  principal  mountain-chains — 
the  Rocky  Mountains  and  the  Appalachians — had  not  yet 
been  made,  and  the  surface  of  the  submerged  land  was 
nearly  flat.  The  fact  that  the  beds  were  really  marine  is 
proved  by  their  containing,  in  most  cases,  sea-shells  or 
corals,  the  relics  of  marine  life ;  and  the  great  extent  of  the 
continental  seas  is  indicated  by  the  beds  covering  areas  of 
tens  of  thousands  of  square  miles,  some  of  them  extending 
from  the  Atlantic  border  westward  beyond  the  Mississippi. 
In  such  great  seas,  having  the  bottom  nearly  flat,  the  de- 
posits made  by  means  of  the  currents  and  waves  would  be 
nearly  or  quite  horizontal.  As  they  increased,  they  would 
near  the  surface ;  and  here  the  action  of  the  waves  would 
level  off  the  upper  surface  of  the  beds,  whether  accumula- 
tions of  sand  or  earth,  or  of  shells  or  corals.  And  if  the 
bottom  were  very  slowly  sinking,  the  accumulations  would 
still  go  on  thickening,  and  the  beds  continue  to  have  the 
same  level  or  horizontal  position. 

Many  strata  have  been  formed  along  the  borders  of  the 
continents ;  and  here,  also,  they  take  horizontal  positions. 
The  bottom  of  the  border  of  the  Atlantic,  south  of  Long 
Island,  is,  for  80  miles  from  the  coast-line,  so  nearly 
horizontal  that,  in  a  distance  outward  of  600  to  700  feet,  it 
deepens  on  an  average  only  1  foot;  and  if  the  area  were 
above  the  ocean,  no  eye  would  detect  that  it  was  not  per- 
fectly level.  It  is  obvious  that  deposits  over  such  a  con- 
tinental border,  as  well  as  those  of  beaches,  would  be  very 
nearly  horizontal. 

The  deltas  about  the  mouths  of  great  rivers,  like  that  of 
the  Mississippi,  cover-sometimes  thousands  of  square  miles. 
They  are  made  of  the  sands  and  earth  brought  down  by  the 
river  and  spread  out  by  the  currents  of  the  river  and  ocean. 


88 


LITHOLOGICAL   GEOLOGY. 


Fig.  33. 


They  are,  therefore,  examples  of  the  deposition  of  rock- 
material  on  a  scale  of  great  extent;  and  various  strata  have 
been  formed  as  deltas  are  formed.  The  beds  of  delta-deposits 
are  always  horizontal  or  nearly  so. 

Other  beds  were  originally  vast  marshes,  like  the  marshes 
of  the  present  day,  only  larger.  Such  was  the  condition  of 
those  beds  in  the  coal-formation  that  contain  coal.  Now, 
marshes  have  a  horizontal  surface;  and  marsh  deposits,  as 
they  accumulate,  have  a  horizontal  structure.  Many  coal- 
beds  contain  stumps  of  trees  (fig.  33) 
rising  out  of  the  coal ;  and  they  always 
stand  vertically  on  the  bed,  however 
much  it  may  be  displaced,  showing 
that  the  bed  was  horizontal  when 
formed,  or  when  the  trees  were  grow- 
ing. 

Exceptions  to  a  horizontal  position. — When  a  river  empties 
into  a  lake  or  sea,  the  bottom  of  which,  near  its  mouth, 
is  very  steeply  inclined,  the  deposits  of  detritus  made  by  the 
river  will  for  a  while  conform  to  the  slope  of  the  bottom, 

Fig.  34. 


as  in  fig.  34.  When  rivers  fall  down  precipices,  they  make 
a  steep  bank  of  earth  at  the  foot,  whose  layers,  if  any  are 
observable,  will  take  the  slope  of  the  bank. 

But  these  and  similar  cases  of  exceptions  to  a  horizontal 
position  are  of  small  extent. 

2.  Dislocations  of  strata. — Most  of  the  strata  of  the  globe 
have  lost  their  original  horizontal  position,  and  are  more 
or  less  inclined ;  some  are  even  vertical  or  stand  on  end. 

They  are  occasionally  bent  or  folded  as  a  quire  of  paper 


DISLOCATIONS    OF    STRATA.  39 

might  be  folded,  only  the  folds  are  miles,  or  scores  Of  miles, 
in  sweep. 

They  have  often  also  been  fractured,  and  the  separated 
parts  have  been  pushed,  or  else  have  fallen,  out  of  their 
former  connections,  so  that  the  portion  of  a  stratum  on  one 
side  of  the  fracture  may  be  raised  inches,  feet,  or  even 
miles,  above  that  on  the  other  side. 

It  is  stated  on  p.  1,  that  a  thickness  of  rock  equal  to  15 
or  18  miles  is  open  to  the  geological  explorer.  This  could 
not  be  true,  were  all  strata  in  their  original  horizontal  posi- 
tion ;  for  the  most  that  would  in  that  case  be  within  reach 
would  not  exceed  the  height  of  the  highest  mountain.  But 
the  upturning  which  the  earth's  crust  has  undergone  has 
brought  the  edges  of  strata  to  the  surface,  and  there  is  hence 
no  such  limit :  however  deep  stratified  beds  may  extend, 
there  is  no  reason  why  the  whole  should  not  be  brought  up 
BO  as  to  be  exposed  to  view  in  some  parts  of  the  earth's 
surface. 

The  following  are  explanations  of  the  terms  used  in 
describing  the  positions  of  strata : — 

1.  Outcrop. — The  portions  or  ledges  of  strata  projecting 
out  of  the  ground,  or  in  view  at  the  surface  (fig.  35). 

2.  Dip. — The  angle  of  slope  of  inclined  or  tilted  strata. 
In  figures  35,  36,  d  p  is  the  direction  of  the  dip.     Both  the 
angle  of  slope  and  the  direction  are  noted  by  the  geologist : 

Fig.  35. 


thus,  it  may  be  said  of  beds,  the  dip  is  50°  to  the  south,  or 
45°  to  the  northwest,  etc. 


40 


LITHOLOGICAL   GEOLOGY. 


When  only  the  edges  of  layers  are  exposed  to  view,  it  is 
not  safe  to  take  the  slope  of  the  edges  as  the  slope  of  the 
layers;  for  in  figure  36  the  edges  on  the  faces  1,  2,  3,  4,  are 
Fig.  36. 


all  edges  of  the  same  beds,  and  only  those  of  the  face  1 
would  give  the  right  dip. 

The  dip  is  measured  by  means  of  instruments  called  clino- 
meters.    In   fig.  37,  a  b  c  d  represents   a   square   block  of 
Fig.  37. 


wood,  having  a  graduated  arc  b  c  and  a  plummet  hung 
below  a.  Placed  on  the  sloping  surface  A  B,  the  position 
of  the  plummet  gives  the  angle  of  dip.  This  kind  of 
clinometer  is  often  made  in  the  form  of  a  watch  and  com- 
bined with  a  compass.  In  the  same  figure,  e  d  f  repre- 
sents another  clinometer.  It  has  a  level  on  the  arm  d  e) 
and  when  the  arm  d  f  is  placed  on  the  sloping  surface, 
the  other  arm  is  raised  until,  as  shown  by  this  level,  it 
is  horizontal ;  the  dip  is  the  angle  between  the  two  arms,  as 
measured  on  the  arc  at  the  joint.  To  avoid  errors  from  the 


Fig.  38. 


DISLOCATIONS    OF    STRATA. 

unevenncss  of  a  rock,  a  board  should  be  laid  down  first,  and 
the  measurement  be  made  on  its  surface. 

3.  Strike. — The  horizontal  direction  at  right  angles  with 
the  dip,  as  s  t  in  fig.  35.    The  direction  of  the  line  of  outcrop 
is  often  the  true  strike. 

4.  Fault. — When  strata  have  been  fractured  and  the  parts 
are  displaced,  as  in  fig.  38,  the 

displacement  is  called  a  fault. 
The  coal-beds  1  and  2  in  this 
figure  are  thus  faulted  in  two 
places;  and  the  amount  of  the 
fault  in  either  is  the  number  of 
feet  or  inches  that  one  part  is 
above  or  below  the  other. 

5.  Folds  or  flexures. — The  rising  or  sinking  of  strata  in 
curving  planes,  as  represented  in  the  following  sections,  fig. 

Fig.  39. 


a// 


39,  A,  B ;  and  in  the  natural  section,  fig.  40,  from  the  Ap- 
palachian Mountains  in  Virginia. 

Fig.  40. 


In  fig.  39.  a  x  is  the  axis  or  axial  plane  of  the  fold. 

6.  Anticlinal. — Having  the  strata  sloping  away  from  a 
common  line  in  opposite  directions,  as  the  layers  either  side 
of  a  x  in  fig.  39,  A  :  the  axis  is  here  called  an  anticlinal  axis; 
and  a  ridge  made  up  of  such  strata  is  an  anticlinal  ridge. 
The  word  anticlinal  is  from  the  Greek  anti,  in  opposite  direc- 
tions, and  klmo,  I  incline. 


42  LITHOLOGICAL   GEOLOGY. 

7.  Synclinal. — Having  the  strata  sloping  towards  a  com- 
mon  line  from  opposite  directions.     In  n'g.  89,  B,  ax,  ax  are 
anticlinal  axes,  and  a'  x',  between  the  others,  a  synclinal  axis; 
or,  viewing  the  former  as  anticlinal  ridges,  the  latter  is  a 
synclinal  valley.     The  word  synclinal  is  from  the  Greek  sun, 
together,  and  klino,  I  incline. 

8.  Monoclinal. — Having  the  strata  sloping  in   only  one 
direction.     A  valley  made  by  the  fracture  of  strata  and  the 
slide  of  one  side  past  the  other,  the  dip  of  the  two  portions 
remaining  unaltered  or  but  little  so,  is  called  a  monoclinal 
valley.     The  word  monoclinal  is  from  the  Greek  monos,  one, 
and  klino. 

9.  Geoclinal. — Having  the   general  mass  of  the   earth's 
crust,  but  not  the  strata,  sloping  at  surface  towards  a  com- 
mon axis  of  depression.    Thus,  a  geodinal  valley  is  a  depres- 
sion of  the  surface  produced  by  an  uplift  of  the  earth's  crust 
on  either  side  of  the  depression,  without  a  simple  synclinal 
dip  in  the  strata  bounding  the  depression, — as  the  Connecti- 
cut Valley,  the  Mississippi  Valley. 

10.  Denudation — Decapitated  Folds. — If  the  top  of  the  fold 
in  fig.  41  were  cut  off  at  a  b,  there  would  remain  the  part 
represented  in  fig.  42,  in  which 

there  is  no  appearance  of  any 

fold,  and  only  a  uniform  series 

of  dips ;  and  although  1',  2',  3', 

might  appear  to  be  the  lower 

strata  of  the   series,   they  are 

actually  parts  of  1,  2,  3.    A  long 

series  of  such  folds  pressed  together,  and  thus  decapitated, 

would  make  a  series  of  uniform  dips  over  a  wide  extent  of 

country. 

The  wear  of  the  ridges  of  a  country  by  water  has  often 
produced  the  effect  here  described  over  regions  of  folded 
rocks. 

In  other  cases,  a  similar  wear  has  removed  the  rocks  over 


UNCONFORMAB1E    STRATA. 


43 


great  areas,  or  filled  up  intermediate  depressions  by  soil :  so 
that  the  rocks  are  visible  only  at  long  intervals  (as  in  fig. 

Fig.  43. 


43),  and  the  faults  which  may  exist  are  concealed  from  view 
Many  of  the  difficulties  connected  with  the  study  of  rocks 
arise  from  this  cause. 

11.  Unconformable  strata. — When  strata  have  been  tilted 
or  folded,  and,  subsequently,  horizontal  beds  have  been  laid 
down  over  them,  the  two  sets  are  said  to  be  unconformable, 

Fig.  44. 


because  they  do  not  conform  in  dip.  It  is  a  case  of  uncon- 
formability  in  the  stratification.  Thus,  in  fig.  44  the  beds  a  b 
are  unconformable  to  those  below  them ;  so  also  the  tilted 
beds  c.  d  are  unconformable  to  those  beneath,  and  the  beds 
ef  to  the  beds  c  d. 

It  is  plain  that  the  folded  rocks  represented  in  figure  44 
are  the  oldest,  and  that  they  were  folded  before  a  b  or  c  d 
were  deposited.  Again,  it  is  evident  that  the  beds  c  d  are 
older  than  the  beds  ef,  and  also  that  they  were  tilted  and 
faulted  before  the  beds  e/were  formed.  Thus  the  geologist 
arrives  at  the  relative  periods  of  occurrences  in  geological 
time.  If  the  precise  age  of  the  three  sets  of  rocks  here 
represented  could  in  any  case  be  ascertained  (as  they  gene- 
rally may  be),  the  periods  of  uplift  would  be  more  precisely 
determined. 

3.  Order  of  Arrangement  of  Strata, 
It   has    been    explained    that   the    strata    are   historical 

5 


44  LITHOLOGICAL    GEOLOGY. 

records  of  past  conditions  of  the  earth's  surface.  In  order, 
therefore,  that  the  records  should  make  an  intelligible  his- 
tory, all  the  parts  should  be  arranged  in  their  proper  order, 
that  is,  the  order  of  time.  The  determination  of  this  order  is 
one  of  the  first  things  before  the  geologist  in  his  exami- 
nations of  a  country. 

Many  difficulties  are  encountered. 

1.  The  strata  of  the  same  period  or  time — called  equivalent 
strata,  because  equivalent  in  age — differ,  even  on  the  same 
continent.    Sandstones  and  shales  were  often  forming  along 
the  Appalachians  in  Pennsylvania  and  Virginia,  when  lime- 
stones were  in  progress  over  the  Mississippi  Valley.     The 
chalk  formation  in  England  contains  thick  strata  of  chalk; 
but  in  North  America  the  same  formation  exists  without 
any  chalk. 

2.  When  rocks  have  been  forming  in  one  region,  there 
have  been  none  in  progress  in  many  others.  Hence  the  series 
of  strata  serving  as  records  of  geological  events  is  nowhere 
perfect.    In  one  country  one  part  will  be  very  complete ;  in 
another,  another  part ;  and  all  have  their  long  blanks, — that 
is,  large  parts  of  the  series  entirely  wanting.    In  New  York 
and  the  States  west  to  the  Mississippi,  there  is  only  part  of 
the  lower  half  of  the  series.    In  New  Jersey  there  is  part  of 
the  lower  half  and  part  of  the  upper  half,  with  wide  breaks 
between.     Over  a  large  part  of  northern  New  York  there  is 
only  the  very  earliest  of  rocks, — those  made  before  the  first 
fossiliferous  beds  were  laid  down. 

The  thickness  of  the  fossiliferous  series  in  the  State  of 
New  York,  south  of  its  centre,  is  about  13,000  feet ;  and  north 
of  its  centre  they  thin  out  to  a  few  feet ;  in  Pennsylvania, 
the  maximum  thickness  is  over  40,000  feet;  in  Indiana 
and  other  adjoining  States  west  and  south,  3500  to  6000 
feet.  In  Great  Britain,  the  whole  thickness  above  the 
unfossiliferous  bottom-rocks  is  about  70,000  feet.  The  thick- 
ness here  given  is  the  sum  of  the  greatest  thickness  of  each 


EQUIVALENCY    OF    ROCKS.  45 

of  the  successive  strata,  and  exceeds  that  existing  at  any  one 
point,  as  one  formation  may  be  thickest  in  one  district,  and 
another  in  a  district  more  or  less  remote. 

3.  The  rocks  of  a  country  are  to  a  great  extent  covered 
with  earth  or  soil,  so  that  they  can  be  examined  only  at 
distant  points. 

4.  The   strata,   in   many   regions,   have   been   displaced, 
folded,  fractured,  faulted,  and  even  crystallized  extensively, 
adding  greatly  to  the  difficulties  in  the  way  of  the  geological 
explorer. 

The  following  are  the  methods  to  be  used  in  determining 
the  true  order  of  arrangement : — 

A.  In  sections  of  the  rocks  exposed  to  view  in  the  sides 
of  valleys  or  ridges,  the  order  should  be  directly  studied, 
and  each  stratum  traced,  as  far  as  possible,  through  all  the 
exposed  sections. 

When,  through  large  intervals,  a  covering  of  soil  or  water 
prevents  the  tracing  of  the  beds,  other  means  must  be  used. 

B.  Thje  aspect  or  composition  of  the  rock  may  help  to 
determine  which   strata   are   identical.     But  this   method 
should  be  used  with  caution,  for  the  reason  stated  above,  in 
§  1, — that  rocks  made  at  the  very  same  time  may  be  widely 
different ;   and,  conversely,  those   made   in  very  different 
periods  may  look  precisely  alike  in  color  and  texture. 

C.  Fossils  afford  the  best  means  of  determining  identity. 
This  is  so  because  of  the  fact,  already  mentioned,  that  the 
fossils  of  an  epoch  are  very  similar  in  genera — if  not  in 
species — the  world  over;  and  those  of  different 'epochs  are 
different. 

As  the  kinds  of  fossils  belonging  to  each  period  and  age 
are  now  pretty  well  known,  and  catalogues  and  figures  have 
been  published,  it  is  only  necessary,  on  commencing  the 
investigation  of  a  stratum,  to  collect  its  fossils,  study  them 
with  care,  and  then  compare  them  with  the  figures  and 
descriptions  to  be  found  in  works  on  the  subject.  In  this 


46  LITHOLOGICAL   GEOLOGY. 

way  it  has  been  proved  that  the  chalk  formation  exists  in 
North  America,  although  there  is  no  chalk  to  be  found.  In 
the  same  manner  the  equivalents  in  America  of  the  rocks  of 
Britain  and  Europe,  Asia,  or  even  Australia,  are  ascertained ; 
for  this  means  of  determination  is  a  universal  one,  applying 
to  the  equivalency  of  rocks  in  different  hemispheres  as  well 
as  on  the  same  continent. 


ANIMAL   AND   VEGETABLE   KINGDOMS.  47 


REVIEW  OF  THE  ANIMAL  AND  VEGETABLE 
KINGDOMS. 

THE  following  pages  on  the  Animal  and  Yegetable  King- 
doms are  inserted  in  this  place  to  prepare  the  student 
for  the  following  portion  of  the  work,  on  Historical  Geology, 
in  which  the  progress  of  life  is  a  prominent  part. 

Distinctions  between  an  Animal  and  a  Plant. 

1.  An  Animal. — An  animal  is  a  living  being,  sustained  by 
nutriment  taken  into  an  internal  cavity  or  stomach,  through 
an  opening  called  the  mouth.  It  is  capable  of  perceiving  the 
existence  of  other  objects,  through  one  or  more  senses.  It 
has  (except  in  some  of  the  lowest  species)  a  head,  which  ia 
the  seat  of  the  power  of  voluntary  motion,  and  which  con- 
tains the  mouth.  It  is  fundamentally  a  fore-and-aft  struc- 
ture, the  head  being  the  anterior  extremity,  and  it  is  typi- 
cally forward-moving.  With  its  growth  from  the  germ, 
there  is  an  increase  in  mechanical  power  until  the  adult  size 
is  reached.  In  the  processes  of  respiration  and  growth,  it 
gives  out  carbonic  acid,  and  uses  oxygen. 

A  Plant. — A  plant  is  a  living  being  sustained  by  nutriment 
taken  up  externally  by  leaves  and  roots.  It  is  incapable  of 
perception,  having  no  senses.  It  has  no  head,  no  power  of 
voluntary  motion,  no  mouth.  It  is  fundamentally  an  up-and- 
down  structure,  and,  with  few  exceptions,7?.m?.  In  its  growth 
from  the  germ  or  seed,  there  is  no  increasing  mechanical 
power.  In  the  process  of  growth,  it  gives  out  oxygen  and 
uses  carbonic  acid. 

5* 


48  ANIMAL    KINGDOM 


I.  ANIMAL  KINGDOM. 
1.  The  Animal  Structure. 

The  nature  of  an  animal  requires,  for  a  full  exhibition  of 
its  powers,  the  following  parts : 

1.  A  stomach  and  its  appendages  to  turn  the  food  into 
blood,  with  an  arrangement  for  carrying  off  refuse  material. 

2.  A  system  of  vessels  for  carrying  this  blood  throughout 
the  body,  so  as  to  promote  growth  and  a  renewal  of  the 
structure. 

3.  A  heart,  or  forcing-pump,  to  send  the  blood  through  the 
vessels. 

4.  A  means  of  respiration,  or  of  taking  air  into  the  system 
(as  by  lungs  or  gills),  because  this  growth  and  renewal 
require  the  oxygen  of  the  air  to  act  in  conjunction  with  the 
blood,  as  much  as  a  fire  requires  air  in  order  that  the  fuel 
may  burn. 

5.  Muscles,  or  contractile  fibres,  to  act  by  contraction  and 
relaxation  in  putting  the  parts  or  members  in  motion. 

G.  A  brain,  or  head-mass  of  nervous  matter,  and  a  system 
of  nerves,  branching  through  the  body,  to  serve  as  a  seat 
for  the  will  and  for  the  power  of  sensation  and  motion,  and 
to  convey  the  determinations  of  the  will  and  sensation 
through  the  body. 

In  the  lowest  form  of  animal  life,  as  some  microscopic 
Protozoans,  the  stomach  is  not  a  permanent  cavity,  but  is 
formed  in  the  mass  of  the  tissue  whenever  a  particle  of  food 
comes  in  contact  with  the  body.  In  other  words,  a  stomach 
is  extemporized  as  it  is  needed.  In  species  of  a  little  higher 
grade,  as  Polyps,  there  is  a  mouth  and  stomach,  with  mus- 
cles, an  imperfect  system  of  nerves  when  any,  and  a  means 
of  respiration  through  the  general  surface  of  the  body;  but 
there  is  no  distinct  heart,  and  the  animal  is  ordinarily  fixed 
to  a  support. 


ANIMAL   KINGDOM.  49 

2.  Subdivisions  of  the  Animal  Kingdom. 

There  are  four  distinct  plans  of  structure  according  to  which 
animals  are  made;  and  the  species  corresponding  to  each 
make  up  what  is  called  a  sub-kingdom  in  the  kingdom  of  ani- 
mals. These  four  sub-kingdoms,  or  plans  of  structure,  are 
the  following : — 

1.  The   VERTEBRATE  :   having  (as  in  Man,  Quadrupeds, 
Birds,   Eeptiles,  and  Fishes)  an  internal  jointed  skeleton, 
of  which  the  back-bone  is  called  the  vertebral  column,  and 
each  of  its  joints  a  vertebra. 

The  remaining  sub-kingdoms  have  no  internal  jointed 
skeleton. 

2.  The  ARTICULATE  :  having  (as  in  Insects,  Spiders,  Crabs, 
Lobsters,  Worms)  the  body  and  its  appendages  (as  the  legs, 
etc.)  articulated,  that  is,  made  up  of  a  series  of  joints. 

3.  The  MOLLUSCAN  :  having  (as  in  the  Oyster,  Clam,  Snail, 
Cuttle-fish)  a  soft,  fleshy  body  without  articulations  or  joints ; 
and  the  appendages,  when  any  exist,  also  without  joints. 
The  name  is  from  the  Latin  mollis,  soft. 

4.  The  RADIATE  :  having  (as  in  the  Polyp,  Medusa,  Sea- 
urchin,  Star-fish)  the  body,  both  externally  and  internally, 
radiate  in  arrangement,  the  parts  being  arranged  radiately 
around  the  mouth  and  stomach, — as  in  a  flower  or  an  orange 
the  parts  are  radiately  arranged  about  its  centre  or  central 
axis. 

Radiate  animals  take  after  the  vegetable  kingdom  in  type 
of  structure  (plants  also  being  radiates};  yet  they  are  strictly 
animals,  as  they  have  a  mouth,  stomach,  and  other  animal 
organs.  The  type  of  structure  in  each  of  the  other  sub- 
kingdoms  is  purely  animal. 

5.  PROTOZOANS. — Besides  the  above,  there  are  other  species 
of  such  extreme  simplicity  that  neither  of  the  systems  of 
structure  above  mentioned  is  apparent  in  them,  and  these 
are,  therefore,  in  a  sense  systemless  animals.   Many  have  not 


50  ANIMAL   KINGDOM. 

even  a  mouth.  They  include  the  Sponges,  and  a  large  num- 
ber of  minute  species,  visible  only  with  the  aid  of  a  micro- 
scope. 

1.   SUB-KINGDOM  OP  VERTEBRATES. 

Class  1. — MAMMALS. — "Warm-blooded  animals  that  suckle 
their  young,  as  Man,  Quadrupeds,  Whales.  Nearly  all  are 
viviparous;  a  few  (as  the  Opossum  and  other  Marsupials) 
are  semi-oviparous,  the  young  at  birth  being  very  immature. 

Class  2. — BIRDS. — Warm-blooded  air-breathing  animals, 
oviparous,  having  a  covering  of  feathers,  and  the  -anterior 
limbs  more  or  less  perfect  wings. 

Class  3. — KEPTILES. — Cold-blooded  air-breathing  animals, 
oviparous,  having  a  covering  of  scales  or  simply  a  naked 
skin.  There  are  two  sub-classes : — 1.  True  Reptiles  (as  Cro- 
codiles, Lizards,  Turtles,  Snakes),  which  breathe  with  lungs 
(or  are  air-breathing)  when  young  as  well  as  afterward, 
being,  in  this  respect,  like  birds  and  quadrupeds;  2.  Amphi- 
bians (as  Frogs  and  Salamanders),  which  breathe  by  means 
of  gills  when  young,  and  afterwards  become  air-breathing, 
the  animal  undergoing  thus  a  metamorphosis. 

Class  4. — FISHES. — Cold-blooded  oviparous  animals,  breath- 
ing by  means  of  gills,  and  having  a  covering  of  scales  or 
simply  a  naked  skin.  There  are  three  prominent  groups  : — 

1.  Teliosts  (as  the  Perch,  Salmon,  and  all  common  fishes), 
having  the  scales  membranous,  the  skeleton  bony,  and  the 
gills  attached  at  only  one  margin. 

The  name  is  from  the  Greek  teleios,  perfect,  and  osteon, 
bone,  alluding  to  the  skeleton  being  bony. 

The  scales  in  many  are  toothed  or  set  with  spines  about 
the  inner  margin  (fig.  50),  while  others  have  the  margin 
smooth  (fig.  49).  Fishes  having  scales  of  the  former  kind,  as 
the  Perch,  have  been  called  Ctenoids  by  Agassiz  (from  the 
Greek  kteis,  comb);  and  those  having  scales  of  the  latter 
kind,  as  the  Salmon,  etc.,  Cycloids  (from  the  Greek  kuklon,  a 
circle). 


FISHES.  51 

2.  Ganoids  (as  the  Gar-pike  and  Sturgeon),  having  the 
scales  bony  and  usually  shining,  and  the  skeleton  often  car- 
tilaginous. The  name  is  from  the  Greek  ganos,  shining. 

Fig.  45  represents  one  of  the  ancient  Ganoids.  The  verte- 
bral column  extends  to  the  extremity  of  the  tail,  so  that  the 
tail-fin  is  vertebrated,  while  in  modern  Gars  and  Teliosts  the 

Fig.  45. 


Palseoniscus  Freicslebeni  (X  l/Q- 


vertebral  column  stops  at  the  commencement  of  the  tail,  or 
the  tail-fin  is  non-vertebrate  (fig.  46).  Agassiz  calls  the  former 


JANOIDS  (excepting  49,  50).— Fig.  46,  Tail  of  Thrissops  (X  \4);  47,  Scales  of  Cheirolopis 
Traillii  (X  12);  48,  Palreoniscus  lepidurus  (X  6);  48  a,  under-view  of  same;  49,  Scale  of  a 
Cycloid ;  50,  id.  of  a  Ctenoid ;  51,  Part  of  pavement-teeth  of  Gyrodus  Umbilicus ;  52,  Tooth  of 
Lepidosteus ;  53,  id.  of  a  Cricodus ;  5-t,  Section  of  tooth  of  Lepidosteus  OSSGUB. 

kind  heterocercal,  and  the  latter  homocercal.    The  scales  are 
either  rhombic,  as  in  figs.  45,  46,  or  rounded.    Some  of  these 


52 


ANIMAL    KINGDOM. 


rhombic  bony  scales  are  shown  in  figs.  47,  48.  The  teeth 
(figs.  52,  53)  often  have  a  folded  or  labyrinthine  texture  or 
arrangement  within,  as  shown  in  fig.  54.  In  one  group,  the 
Ganoids  have  a  pavement  of  teeth  in  the  mouth,  as  in  fig.  51. 
3.  Selachians  (as  the  Sharks  and  Rays),  having  a  hard 
skin,  often  rough  with  minute  points,  the  skeleton  more  or 

Figs.  55-65. 


SELACHIANS.— Fig.  55,  Spinax  Blainvillii  (X  H);  56.  sPine  of  anterior  dorsal  fin,  natural  size; 
57,  Cestracion  Philippi  (X  %);  58,  Tooth  of  Lamna  elegans;  59,  Tooth  of  Carcharodon  an- 
gustidens;  60,  Notidanus  primigenius;  61,  Hybodus  minor;  62,  Hyb.  plicatilis;  63,  Mouth 
of  Cestracion,  showing  pavement-teeth  of  lower  jaw;  64,  Tooth  of  Acrodus  minimus;  65, 
Tooth  of  Acrodus  nobilis. 

less  completely  cartilaginous,  and  the  .gills  attached  by  both 
margins.     The  name  is  from  the  Greek  selachos,  cartilage. 


ARTICULATES.  53 

Fig.  55  represents,  much  reduced,  one  of  the  order  (a 
Spinax},  having  the  mouth,  as  usual,  on  the  under  surface 
of  the  head,  and  remarkable  for  the  spine  before  each  of  the 
back  fins  :  one  of  the  spines  is  shown,  natural  size,  in  fig.  56. 
Fig.  57  is  an  outline  of  another  Selachian,  of  the  genus  Ces- 
tracion,  living  in  the  vicinity  of  Australia,  peculiar  in  having 
the  mouth  at  the  extremity  of  the  head,  and  also  in  the 
teeth  of  the  mouth  having  in  part  the  form  and  appearance 
of  a  pavement,  as  shown  in  fig.  63.  Figs.  58  to  62  are  teeth 
of  different  Selachians  related  to  the  Sharks ;  and  figs.  64, 
65,  pavement-teeth  of  Cestraciont  species.  The  Cestraciont 
Selachians  were  once  very  common ;  but  now  the  only  living 
species  known  are  confined  to  Australasia. 

2.  SUB-KINGDOM  OF  ARTICULATES, 

Among  Articulates  there  are  three  classes ;  one,  including 
the  species  adapted  to  live  on  land,  and  which,  for  this  pur- 
pose, breathe  by  means  of  air-vessels  branching  through  the 
body,  and  two,  of  species  adapted  to  live  in  water,  and, 
therefore,  having  gills. 

1.  LAND-ARTICULATES,  or  the,  class  of  Insecteans.    There 
are  three  orders  or,  grand  divisions  of  Insecteans :  namely, 
1.  Insects;  2.  Spiders;  3.  Myriapods  (or  Centipedes). 

2.  WATER-ARTICULATES,   including    the    two    classes— 1. 
Crustaceans  (as  Crabs,  Lobsters,  etc.),  and  2.  Worms. 

Crustaceans.- — A  knowledge  of  the  principal  subdivisions 
of  Crustaceans  is  especially  important  to  the  student  in 
geology.  There  are  three  orders  : — 

1.  The  Decapods,  or  W-footed  species,  as  the  Crab  (fig.  67), 
Jjpbster,  Shrimp. 

2.  The  Tetradecapods,  or  14-footed  species,  as  the  Sow-bug 
(fig.  68),  found  in  damp  places  under  logs,  the  Sand-flea  of 
sea-shores  among  drift  sea-weed  (fig.  69),  etc. 

3.  The  Entomostracans,  or  inferior  species,  having  the  feet 
defective,  as  the  Cyclops  and  related  species  (figs.  71,  72), 


54 


ANIMAL    KINGDOM. 


Daphnia,  Limulus  or  Horse-shoe,  the  Cypris,  and  other  Ostra- 
coids  (fig.  74).     These  Ostracoids  are  generally  minute  spe- 


Figs.  66-75, 


ABTICULATES. — 1.  Worms:  66,  Arenicola  piscatorum,  or  Lob-worm  (X  Y&>-  2.  Crustaceans: 
67,  Crab,  species  of  Cancer;  68,  an  Isopod,  species  of  Porcellio;  69,  an  Amphipod,  species 
of  Orchestia;  70,  an  Isopod,  species  of  Serolis  (X  K)?  71>  72>  Sapphirina  Iris;  71,  female, 
72,  male  (X*6);  73,  Trilobite,  Calymene  Blumenbachii ;  74,  Cythere  Americana,  of  the 
Ostracoid  famUy  (X  12) ;  75,  Anatifa,  of  the  Cirriped  tribe. 

cies,  having  a  shell  like  that  of  a  bivalve  Mollusk,  as  fig.  74 
shows;  but  inside  of  the  shell,  instead  of  an  animal  like  a 
clam,  there  is  one  more  like  a  shrimp,  with  jointed  legs.  The 
name  is  from  the  Greek  ostrakon,  shell,  the  word  from  which 
oyster  is  derived. 

Among  Entomostracans,  there  are  also  the  Barnacles  and 
other  Cirripeds,  one  of  .which  is  represented  in  fig.  75. 

Trilobites  (fig.  73)  are  Crustaceans  related  to  the  Ento- 
mostracans,  though  more  like  the  Tetradecapods  (figs.  68,  70) 
in  form.  They  may  be  intermediate  between  the  two  orders. 
The  tribe  is  now  extinct. 

3.  SUB-KINGDOM  OF  MOLLUSKS. 

There  are  two  grand  divisions  or  classes  of  Mollusks : — 
1.  The  Ordinary  Mollusks,  as  the  Clam.  Snail,  and  Cuttlefish; 
and,  2,  the  plant-like  or  Anthoid  Mollusks,  many  of  which  are 
attached  by  stems,  like  flowers,  and  some  have  an  external 


MOLLUSKS. 


55 


resemblance   to   flowers    (figs.  84,  85),  though   not   radiate 
internally  like  true  Radiate  animals. 

1.  Ordinary  Mollusks. — There  are  three  orders : — 1.  Cepha- 
lopods:  having  the  head  surrounded  by  arms,  and  largo 
eyes ;  the  shell,  when  any  exists  as  an  external  covering  for 
the  body,  is,  with  a  rare  exception,  divided  internally  by 


Figs.  76-85 


MOLLUSKS. — 1.  Cephalapods :  fig.  76,  Nautilus,  showing  the  partitions  in  the  shell  and  thfc 
animal  in  the  outer  chamber. — 2.  Gastropods :  77,  Helix. — 3.  Ptercpids:  78,  Cleodora. — 1 
Cmchifers:  79,  £0;  81,  the  oyster.— 5.  firacfiiopnds :  82,  Lingula,  on  its  stem;  83,  Tere. 
bratula,  showing  the  aperture  from  which  the  stem  for  attachment  passes  out. — 6.  Bryo- 
zoans:  84,  Eschara.with  the  animals  a  little  enlarged;  85,  one  of  the  animals  out  of  tha 
shell,  more  enlarged. 

cross-partitions  into  a  series  of  chambers,  whence  they  are 
called  chambered  shells,  as  in  the  Nautilus  (fig.  76)  and  Am- 
monite (fig.  282).  A  few  have  an  internal  chambered  shell ; 
others  an  internal  straight  bone,  which  has  sometimes  a 
conical  cavity.  The  name  is  from  the  Greek  kephale,  head, 
and  pous,  foot. 

.  2.  Cephalates:  having  a  head  with  distinct  eyes,  but  no 
arms  around  it,  and  usually  a  spiral  shell,  if  any;  as  the 
Snail  (fig.  77)  and  other  Univalves.  The  name  is  from  the 


56  ANIMAL   KINGDOM. 

Greek  kephale,  head.  The  species  of  one  division — that  con- 
taining the  Snail  and  all  ordinary  Univalves — are  called 
Gasteropoda,  from  the  Greek,  implying  that  they  crawl  on 
their  belly, — this  part  acting,  therefore,  as  a  foot.  In  an- 
other division,  they  have  a  pair  of  wing-like  oars  for  swim- 
ming, and  these  are  called  Pteropods  (fig.  78),  from  the  Greek 
pteron,  wing,  and  pous,  foot. 

8.  Acephals :  having  no  prominent  head,  and  only  imper- 
fect eyes  if  any ;  and  the  shell  commonly  of  two  parts  called 
valves,  whence  the  common  name  of  most  of  the  species, 
Bivalves,  as  the  oyster,  clam  (figs.  79-81).  These  species  are 
called  Conchifers,  from  the  Latin  concha,  shell,  and/ero,  I  bear. 
They  have  thin  lamellar  gills  either  side  of  the  body,  whence 
they  are  often  called  also  Larnellibranchs,  from  lamella,  a 
plate,  and  branchia,  a  gill. 

In  fig.  79,  showing  the  inside  of  a  valve,  1, 2  are  impressions 
of  the  two  great  muscles  by  which  the  animal  closes  the 
shell,  and  p  p  is  the  impression  of  the  margin  of  the  mantle 
or  pallium,  and  called  the  pallial  impression.  This  mantle 
is  a  thin  membrane  lying  next  to  the  shell  j  the  gills  are 
between  it  and  the  body  of  the  Mollusk.  In  fig.  80,  the 
pallial  impression  p  p  has  a  deep  bend  or  sinus  opening 
towards  the  back  margin  of  the  valve.  Shells  having  this 
sinus  in  the  impression  are  described  as  sinupallial,  and 
those  without  it  as  integripallial.  In  fig.  81,  of  the  oyster, 
there  is  but  one  large  muscular  impression  (at  2). 

2.  Anthoid  Mollusks.— These  are  of  three  orders : — 

1.  Braehiopods :  species  (figs.  82,  83)  having  a  bivalve 
shell,  like  the  Conchifers,  but  one  whose  form  is  sym- 
metrical either  side  of  a  middle  line ;  that  is,  if  a  line  be 
dropped  from  the  beak  to  the  opposite  edge  (as  from  b  to  a 
in  fig.  83),  the  parts  of  the  shell  on  the  two  sides  of  the  line 
will  be  equal.  A  line  similarly  drawn  in  the  Conchifers. 
divides  the  valve  unequally  (as  in  fig.  79).  The  animals  have 
two  spiral  arms  within,  which  serve  as  gills.  The  name 


RADIATES. 


57 


Brachiopod,  from  the  Greek  brachion,  arm,  and  pous,  foot, 
refers  to  these  arms. 

2.  Ascidians :  species  with  a  leathery  or  fleshy  exterior, 
and  no  shell,  and  hence  hardly  recognized  among  fossils. 

3.  Bryozoans :  species  of  minute  size,  making  often  cellular 
corals  which,  though  often  in  thin  plates  or  incrustations, 
sometimes  delicately  branch  like  a  moss,  whence  the  name, 
from  the  Greek  bruon,  moss,  and  zoon,  animal.     They  include 
the  Cellepores,  Flustras,  etc. 

4.  SUB-KINGDOM  OF  RADIATES. 
There  are  three  grand  divisions  of  Radiates : — 

90  Figs.  86-95. 


RADIATES.— 1.  Echinoderms:  86,  Echinus,  the  spines  removed  from  half  the  surface  (X  %); 
87,  Star-fish,  Palreaster  Niagarensis;  88,  Crinoid,  Encrinus  liliiformis;  89,  Crinoid,  of  the 
family  of  Cystideans,  Callocystites  Jewettii.— 2.  Acalephs:  90,  a  Medusa,  genus  Tiaropsis: 
91,  Hydra  (X  8);  92,  Syncoryna.— 3.  Polyps:  Fig.  93,  an  Actinia;  94,  a  coral,  Dendrophyl- 
lia ;  95,  part  of  a  branch  of  a  coral  of  the  genus  Gorgonia,  showing  one  of  the  polyps 
expanded. 

1.  Echinoderms  (figs.  86-89) :  having  a  more  or  less  hard 
exterior,  which  is  often  covered  with  spines — whence  the 


58  ANIMAL   KINGDOM. 

name,  from  echinus,  a  hedgehog,  and  derma,  skin.  The  mouth 
opens  downward  in  all  species  except  the  Crinoids.  Among 
them  there  are — (1)  Echinoids,  in  which  the  exterior  is  a  solid 
shell  covered  with  spines,  and  the  mouth  opens  downward 
(fig.  86 — the  spines  are  removed  from  half  of  the  shell) ;  (2) 
The  Asterioids,  or  Star-fishes,  in  which  the  exterior  is  rather 
stiff,  but  still  flexible,  so  that  the  animal  flexes  it  in  its 
movements  (fig.  87) ;  (3)  Crinoids,  which  are  much  like  Star- 
fishes, but  have  a  stem  like  a  flower  (figs.  88,  89). 

2.  Acalephs  (figs.  90-92):    having   a   soft,  flexible   body, 
usually  of  a  jelly-like  aspect,  though  rather  tough,  and  mov- 
ing, when  free,  with  the  mouth  downward,  as  the  Medusce 
(fig.  90).    Some  of  the  species  called  Hydroid  Acalephs  (figs. 
91,  92),  in  one  of  their  stages,  if  not  through  all,  look  like 
Polyps ;  and  some  of  these  Acalephs  form  corals,  like  the 
Polyps.     The  other  species  are  too  soft  to  be  common  as 
fossils. 

3.  Polyps  (figs.  93-95) :  having  a  soft  body  usually  attached 
to  a  support ;  a  mouth  opening  upward ;  one  or  more  rows 
of  tentacles  arranged  about  the  margin  of  a  disk  (somewhat 
like  the  petals  of  an  Aster  around  its  central  disk) ;  and  the 
mouth  situated  at  the  centre  of  the  disk,  as  in  fig.  93.    Most 
corals  are  made  by  Polyps.    The  coral  is  secreted  within  the 
polyp  in  the  same  manner  as  bones  are  secreted  within  other 
animals.  Figs.  94, 95  represent  portions  of  living  corals  with 
the  polyps  expanded.    The  number  of  rays  in  the  cells  of 
modern  corals — called  Actinoids — is  a  multiple  of  six;  and 
that  in  the  more  ancient  corals,  called  Cyathophylloids,  is  a 
multiple  of  four. 

5.  PROTOZOANS. 

The  principal  groups  of  Protozoans  important  to'  the 
geologist  are  three  : — 

1.  The  Sponges.  The  sponges  contain  in  their  tissues 
great  numbers  of  minute  spicules,  which  are,  in  nearly  all 
species,  siliceous;  and  these  siliceous  spicules  are  found  fossil 


ANIMAL    KINGDOM. 


59 


2.  The  fihizopods,  which  make  minute  calcareous  shells 
consisting  usually  of  many  combined  cells.  They  are  often 
called  Polythalamia,  from  their  many  cells,  and  Foraminifera, 
from  the  existence  of  minute  perforations  through  the  shells'. 
Some  of  the  species,  magnified  from  10  to  20  times  (except- 
ing the  last  two,  which  are  natural  size),  are  represented  in 
figs.  96-109. 

Figs.  96-109. 


RHIZOPODS. — Fig.  96,  Orbulina  universa;  97,  Globigerina  rubra;  98,  Textilaria  globulosa 
Ehr.;  99,  Rotalia  globulosa;  99  a,  Side-view  of  Rotalia  Boucana;  100,  Grammostomum 
phyllodes  Ehr. ;  101,  Frondicularia  annularig ;  102,  Triloculina  Josephina ;  103,  Nodosaria 
vulgaris;  101,  Lituola  nautiloides;  105,  a,  Flabellina  rugosa;  106,  Chrysalidina  gradata; 
107,  o,  Cuueolina  Pavonia;  108,  Nummulites  nummularia ;  103  a,  6,  Fusulina  cylindrica. 

3.  Polycystines,  which  make  minute  siliceous  shells,  con- 
sisting of  many  united  cells  (figs.  110-112).      They  differ 

Figs.  110-112. 


POLTCTSTISES. — Fig.  110,  Lychnocannim   Lucorna  (X  100) ;  111,   Eucyrtidium  Mongolfieri 
(X  100; ;  112,  Ilalicalyptra  fimbriata  (X  75). 

from  the  Rhizopods,  further,  in  having  the  arrangement  of 
the  cells  radiate,  and  not  spiral  or  alternate. 
6* 


CRYPTOGAMS. 


II.  VEGETABLE  KINGDOM. 

The  vegetable  kingdom  is  not  divisible  into  sub-kingdoms 
lite  the  animal;  for  all  the  species  belong  to  one  grand  type, 
the  Radiate,  the  one  which  is  the  lowest  of  those  in  the  ani- 
mal kingdom.  The  higher  subdivisions  are  as  follow : — 

I.  CRYPTOGAMS. — Having  no  distinct  flowers  or  proper 
fruit,  the  so-called  seed  being  only  a  spore,  that  is,  a  simple 
cellule  without  the  store  of  nutriment  (albumen  and  starch) 
around  it  which  makes  up  a  true  seed ;  as  Ferns,  Sea- weed. 
They  include — 

1.  Thallogens. — Consisting  wholly  of  cellular  tissue ;  grow- 
ing in  fronds  without  stems,  and  in  other  spreading  forms ; 
as  (1)  Alga?,  which  include  Sea-weeds  and  also  the  Conferva 
or   frog-spittle,  and    many  allied    fresh-water   plants;    (2) 
Lichens,  the  dry  grayish-white  and   grayish-green   plants 
that  cover  stones,  logs,  &c. 

The  Marine  Algce,  or  Sea-weeds,  that  are  found  fossil,  and 
are  not  microscopic  in  size,  are  mostly  of  the  tough  leathery 
kinds,  related  to  the  modern  Fuci.  They  are  often  called 
by  the  general  term  of  Fucoids,  signifying  resembling  Fuci. 

2.  Anogens. — Consisting  wholly  of  cellular  tissue;  growing 
up  in  short,  leafy  stems;  as  (1)  Musci,  or  Mosses;  (2)  Liver- 
worts. 

3.  Acrogens. — Consisting  of  vascular  tissue  in  part,  and 
growing  upward;  as  (1)  Ferns  or  Brakes;  (2)  Lycopodia 
(Ground-Pine) ;  (3)  Equiseta  (Horse-tail  or  Scouring  Rush) ; 
and  including  many   genera  of  trees   of  the   Coal   period 
related  to  these  groups. 

The  Microscopic  Algae  are  sometimes  called  Protophytes. 
They  are  mostly  one-celled  species  :  a  few  consist  of  a  small 
number  of  cells  united ;  and  these  pass  into  other  species, 
like  common  mould,  which  are  in  threads,  simple  or  branched, 
made  up  of  many  cells.  The  kinds  found  fossil  are  the  fol- 
lowing : — 


VEGETABLE    KINGDOM. 


(51 


1.  Diatoms. — Species  having  a  siliceous  shell,  often  quite 
beautiful  in  form.   Some  of  the  shells  are  represented,  highly 
magnified,  in  figs.  117  to  122.     They  grow  so  abundantly  in 
some  waters,  fresh  or  salt,  as  to  produce  large  siliceous  beds, 
the  material  of  which  is  an  excellent  polishing  powder  and 
has  long  been  used  for  this  purpose. 

2.  Desmids. — Species  making  no  siliceous  shell,  consisting 
of  one  or  more  greenish  cells  (figs.  181  to  187,  p.  110).    These 
are  found  fossil  in  flint  and  hornstone. 

II.  PHENOGAMS. — Having  (as  the  name  implies)  distinct 
flowers  and  seed ;  as  the  Pines,  Maple,  and  all  our  shade  and 
fruit  trees,  and  the  plants  of  our  gardens.  They  are  divided 
into — 

1.  Gymnosperms. — Having  the  flowers  exceedingly  simple, 
and  the  seed  naked, — the  seed  being  ordinarily  on  the  inner 
surface  of  the  scales  of  cones,  and  the  wood  having  a  bark 
and  rings  of  annual  growth  (fig.  113);  as  the  Pine,  Spruce, 
Hemlock,  etc.  The  name  Gymnosperm  is  from  the  Greek 
for  naked  seed. 

Figs.  113-122. 
15  14 


PLANTS. — Fig.  113,  section  of  exogenous  wood ;  114,  fibres  of  ordinary  coniferous  wood  (Pinus 
Strobus),  longitudinal  section,  showing  dots,  magnified  300  times ;  115,  same  of  the  Austra- 
lian conifer,  Araucaria  Cunninghami;  116,  section  of  endogenous  stem. 

Figs.  117  to  122,  EIATOMS  highly  magnified ;  117,  Pinnularia  peregrina,  Richmond,  Va. ;  118, 
Pleurosigma  augulatum,  id. ;  119,  Actinoptychus  senarius,  id. ;  120,  Melosira  sulcata,  id  ; 
a,  transverse  section  of  the  same;  121,  Grammatophora  marina,  from  the  salt  water  at 
Stonington,  Conn. ;  122,  Bacilluria  paradoxa,  West  Point. 

-   The  Gymnosperms  include  (1)  the  Conifers,  or  the  Pine- 
tribe  of  plants,  usually  called  evergreens;  and  (2)  the  Cycads, 


62  PHENOGAMS. 

or  plants  related  to  the  Cycas  and  Zamia,  which  have  the 
leaves  and  look  of  a  Palm  page  167),  although,  in  fruit  and 
wood,  true  Gymnosperms.  There  is  a  third  group  of  extinct 
sjfccies  (which  have  not  existed  since  the  Carboniferous  age), 
called  Sigillarice  (see  p.  128). 

The  wood  of  the  Conifers  is  simply  woody  fibre  without 
ducts,  and  in  this  respect,  as  well  as  in  the  flowers  and  seed, 
this  tribe  shows  its  inferiority  to  the  following  subdivision. 
The  fibres,  moreover,  may  be  distinguished,  even  in  petrified 
specimens,  by  the  dots  along  their  surface  as  seen  under  a 
high  magnifier.  The  dots  look  like  holes,  though  really  only 
thinner  spaces.  Fig.  114  shows  these  dots  in  the  Pinus 
Strobus.  In  other  species  they  are  less  crowded.  In  one 
division  of  the  Conifers,  called  the  Araucarice,  of  much  geo- 
logical interest,  these  dots  on  a  fibre  are  alternated  (fig.  115), 
and  the  Araucarian  Conifers  may  thus  be  distinguished. 

2.  Angiosperms. — Having  regular  flowers  and  covered  seed; 
growth  exogenous,  the  plants  having  a  bark  and  rings  of 
annual  growth  (fig.  113)  j  as  the  Maple,  Elm,  Apple,  Rose,  and 
most  of  the  ordinary  shrubs  and  trees.  These  plants  are 
called  Angiosperms,  because  the  seeds  are  in  seed-vessels  ;  and 
also  Dicotyledons,  because  the  seed  has  two  cotyledons  or 
lobes. 

The  Gymnosperms  and  Angiosperms  make  up  the  division 
of  plants  called  Exogens,  which  is  so  named  from  the  Greek 
exo,  outward,  and  gennao,  to  grow,  because  growth  takes  place 
through  annual  additions  of  layers  to  the  outside  of  the  trunk 
between  the  wood  and  the  bark,  as  illustrated  in  fig.  113. 

3  *  Endogens. — Having  regular  flowers  and  seed ;  growth 
endogenous,  the  plants  being  without  bark,  and  showing,  in 
a  transverse  section  of  a  trunk,  the  ends  of  fibres,  and  no 
rings  of  growth  (fig.  116^;  as  the  Palms,  Rattan,  Reed, 
Grasses,  Indian  Corn,  Lily.  The  Endogens  are  Monocotyle- 
dons ;  that  is,  the  seed  is  undivided,  or  consists  of  but  one- 
cotyledon. 


PART  III. 

HISTORICAL    GEOLOGY. 


HISTORICAL  GEOLOGY  treats  of  the  order  of  succession  in 
the  strata  of  the  earth's  crust,  and  of  the  changes  that  were 
going  on  during  the  formation  of  each  bed  or  stratum, — that 
is.  of  the  changes  in  the  oceans  and  the  land;  of  the  changes 
in  the  atmosphere  and  climate ;  of  the  changes  in  the  plants 
and  animals.  In  other  words,  it  is  a  historical  view  of  the 
events  that  took  place  during  the  earth's  progress,  derived 
from  the  study  of  the  successive  rocks.  It  is  sometimes 
called  stratigraphical  geology ;  but  this  term  embraces  only 
a  description  of  the  nature  and  arrangement  of  the  earth's  strata. 

By  using  the  means  for  determining  the  order  of  the 
several  formations  mentioned  on  page  44,  and  by  a  careful 
study  of  the  organic  remains  (as  fossils  are  often  called) 
contained  in  the  rocks,  from  the  oldest  to  the  most  recent, 
it  has  been  found  that  a  number  of  great  ages  in  the  progress 
of  this  life,  and  in  other  events  of  the  history,  can  be  made 
out. 

The  following  have  thus  been  ascertained  : 

(1.)  There  vf  as  first  an  age,  or  division  of  time,  when  there 
was  no  life  on  the  globe ;  or,  if  any  existed,  this  was  true 
only  in  the  later  part  of  the  age,  and  the  life  was  probably 
of  the  very  simplest  kinds. 

(2.)  There  was  next  an  age  when  Shells  or  Mollusks, 
Corals,  Crinoids,  and  Trilobites,  abounded  in  the  oceans, 
when  the  continents  were  almost  all  beneath  the  salt  waters, 

83 


64  HISTORICAL   GEOLOGY. 

and  when  there  was,  as  far  as  has  been  ascertained,  no  ter- 
restrial life. 

(3.)  There  was  next  an  age  when,  besides  Shells,  Corals, 
Crinoids,  Trilobites,  and  Worms,  there  were  Fishes  in  the 
waters,  and  when  the  lands,  though  yet  small,  began  to  be 
covered  with  vegetation. 

(4.)  There  was  next  an  age  when  the  continents  were  at 
many  successive  times  largely  dry  or  marshy  land,  and  the 
land  was  densely  overgrown  with  trees,  shrubs,  and  smaller 
plants,  of  the  remains  of  which  plants  the  great  coal-beds 
were  made.  In  animal  life  there  were,  besides  the  kinds 
already  mentioned,  various  Amphibians  and  some  other 
Eeptiles  of  inferior  tribes. 

(5.)  There  was  next  an  age  when  Reptiles  were  exceed- 
ingly abundant,  far  outnumbering  and  exceeding  in  variety, 
and  many  also  in  size  and  even  in  rank,  those  of  the  present 
day. 

(6.)  There  was  next  an  age  when  the  Reptiles  had  dwin- 
dled, and  Mammals  or  Quadrupeds  were  in  great  numbers 
over  the  continents;  and  the  size  of  these  Quadrupeds,  like 
that  of  the  Reptiles  in  the  preceding  age,  was  far  greater 
than  the  size  of  modern  species. 

(7.)  After  this  came  Man;  and  the  progress  of  life  here 
ended. 

The  above-mentioned  ages  in  the  progress  of  life  and  the 
earth's  history  have  received  the  following  names : — 

1.  Azoic  TIME  or  AGE. — The  name  is  from  the  Greek  a, 
not  or  without,  and  zoe,  life. 

2.  AGE  OF  MOLLUSKS,  or  the  SILURIAN  AGE. 

3.  AGE  OF  FISHES,  or  the  DEVONIAN  AGE. 

4.  AGE  OF  COAL-PLANTS,  or  the  CARBONIFEROUS  AGE. 

5.  AGE  OF  REPTILES,  or  the  REPTILIAN  AGE. 

6.  AGE  OF  MAMMALS,  or  the  MAMMALIAN  AGE. 

7.  AGE  OF  MAN. 

The  first  of  these  ages — the  Azoic — stands  apart  as  the 


SUBDIVISIONS   IN    THE    HISTORY.  65 

preparatory  time  for  the  commencement  of  the*  systems  of 
life.  The  next  three  ages  were  alike  in  many  respects, — 
especially  in  the  air  of  antiquity  pervading  the  tribes  that 
then  lived,  the  shells,  crinoids,  corals,  fishes,  coal-plants,  and 
reptiles  belonging  to  tribes  that  are  now  wholly  or  nearly 
extinct.  The  era  of  these  ages  has,  therefore,  been  appro- 
priately called  Paleozoic  time,  the  word  Paleozoic  coming  from 
the  Greek  palaios,  ancient,  and  zoe,  life. 

The  next  age  was  ushered  in  after  the  extinction  of  many 
of  the  Paleozoic  tribes;  and  its  own  peculiar  life  approxi- 
mated more  to  that  of  the  existing  world.  Yet  it  was  still 
made  up  wholly  of  extinct  species,  and  the  most  prominent 
of  the  tribes  and  genera  disappeared  before  or  at  its  close. 
This  age  corresponds  to  Medieval  time  in  geological  history, 
and  is  called  Mesozoic  time,  from  the  Greek  mesos,  middle,  and 
zoe,  life. 

The  next  age  was  decidedly  modern  in  the  aspect  of  its 
species,  the  higher  as  well  as  lower,  although  only  a  few  of 
those  of  its  later  epochs  survive  into  the  age  of  Man.  It  is 
called  Cenozoic  time,  from  the  Greek  kainos,  recent,  and  zoe, 
life  (the  ai  of  Greek  words  always  becoming  e  in  English, — 
as,  for  example,  in  ether,  from  the  Greek  aithef). 

The  following  are,  then,  the  grand  divisions  of  geological 
time  adopted : — 
I.  Azoic  TIME. 

II.  PALEOZOIC  TIME,  including  (1)  The  Age  of  Mollusks, 
or  Silurian;  (2)  The  Age  of  Fishes,  or  Devonian;  (3)  The 
Age  of  Coal-Plants,  or  Carboniferous. 

III.  MESOZOIC  TIME,  including  the  Keptilian  Age. 

IV.  CENOZOIC  TIME,  including  the  Mammalian  Age. 
V.  The  AGE  OP  MIND,  or  the  Human  Era. 

The  following  sections  represent  the  successive  formations 
of  the  globe,  arranged  in  the  order  of  time,  with  the  subdi- 
visions corresponding  to  the  Ages  and  Periods. 

The  various  strata  in  the  formations  of  an  age  are  very 


Ago. 


HISTORICAL    GEOLOGY. 
Fig.  123 — Paleozoic.  American  Periods.          Furrign  Divtsiont. 


SUBDIVISIONS   IN    THE   HISTORY  67 

Fig.  123  (continued).  Periods.  Foreign  Subdivisions. 


diversified  in  character,  limestones  being  overlaid  abruptly 
by  sandstones,  conglomerates,  or  shales,  or  either  of  these 
last  by  limestones ;  and  each  may  be  very  different  from  the 
following  in  its  fossils.  These  abrupt  transitions  in  the 
strata  are  proofs  that  there  were  great  changes  at  times  in 
the  conditions  of  the  region  where  the  strata  were  formed, 
and  the  transitions  in  the  kinds  of  fossils  are  evidence  of 
7 


68  HISTORICAL   GEOLOGY. 

great  destruction  at  intervals  in  the  life  of  the  seas.  Such 
transitions,  therefore,  naturally  divide  off  the  ages  into 
smaller  portions  of  time,  or  periods,  as  they  are  called.  By 
transitions  similar  in  kind,  but  not  so  great,  periods  may 
often  be  subdivided  into  still  smaller  parts,  or  epochs. 

In  the  preceding  sections,  Azoic  is  at  the  bottom,  on  the 
left;  above  it  there  are  the  names  Silurian,  Devonian,  and  so 
on;  and  the  names  of  the  Periods,  Potsdam,  Trenton,  etc., 
dividing  off  these  Ages,  on  the  right. 

The  names  of  the  Periods  in  the  first  part  of  the  section 
(those  of  the  Paleozoic}  are  derived  from  the  names  of  Ame- 
rican rocks.  The  names  on  the  other  part  are  mostly  Euro- 
pean, as  the  series  of  rocks  it  contains  (those  of  ATesozoic  and 
Cenozoic  time)  are  more  complete  in  Europe  than  in  America, 

The  map  on  page  69  represents  the  distribution  of  the  rocks 
of  the  different  ages,  as  surface-rocks,  over  the  United  States 
and  Canada. 

The  Azoic  areas  are  dotted  with  short  lines. 

The  Silurian  are  lined  horizontally. 

The  Devonian  are  lined  vertically. 

The  Carboniferous  are  black,  or  black  cross-lined  or  dotted 
with  white,  the  black  areas  being  of  the  Carboniferous  period; 
the  cross-lined  of  the  Subcarboniferous;  the  dotted,  of  the 
Permian. 

The  Mesozoic  have  lines,  or  lines  of  dots,  inclined  from  the 
right  above  to  the  left  below,  thus  (/) ;  the  areas  with  lines 
being  Triassic  or  Jurassic,  and  those  with  lines  of  dots  Cre- 
taceous. 

The  Cenozoic  have  lines  inclined  from  the  left  above  to  the 
right  below,  thus  (\);  the  areas  more  openly  lined  on  the 
left  border  of  the  map  are  of  fresh-water  or  brackish- 
Water  origin,  and  the  rest  mainly  of  marine  origin. . 

The  areas  left  white  are  of  unascertained  or  doubtful  age. 

The  Silurian  strata  may  underlie  the  Devonian,  and  both 
Silurian  and  Devonian  the  Carboniferous.  The  black  areas 


SUBDIVISIONS    IN    THE    HISTORY. 


69 


70 


HISTORICAL   GEOLOGY. 


of  the  Carboniferous  period  do  not,  therefore,  indicate  the 
absence  of  Devonian  and  Silurian,  but  only  that  the  Car- 
boniferous strata  are  the  surface  strata  over  the  region. 
There  may  even  be  exceptions  to  this  remark  with  regard 
to  the  surface  strata;  for  over  the  areas  thus  marked  Car- 
boniferous, older  rocks  may  occur  in  some  of  the  bluffs  along 
the  valleys,  or  occupy  small  areas  in  the  region,  which  are 
too  limited  to  be  noted  on  so  small  a  map. 

The  map  on  page  71  represents  the  surface-rocks  of  the 
State  of  New  York  and  Canada,  the  several  areas  corre- 
sponding to  the  periods.  For  the  Silurian,  the  lines  or  dots 
are  drawn  horizontally,  as  in  the  preceding,  and  for  the 
Devonian,  vertically.  There  is  no  Carboniferous,  except  near 
the  southern  border  of  the  State  of  New  York. 

No.  1.  The  Azoic. 

2.  The  Primordial,  or  Potsdam  Period. 

3.  The  Trenton  Period. 

4.  The  Hudson  Period. 

5.  The  Niagara  Period. 

6.  The  Salina  Period. 

9.  The  Upper  Helderberg  Period. 

10  The  Hamilton  Period. 

11  The  Chemung  Period. 
12.  The  Catskill  Period. 

Fig.  125. 


Lower 
Silurian. 

Upper 
Silurian. 


Devonian 


Carboni-  Devonian, 

feroos. 


SUBDIVISIONS   IN   THE    HISTORY. 


71 


Geological  Map  of  New  \«rk  and  Canada. 


72  AZOIC   AGE. 

In  the  section  in  fig.  125,  the  rocks  of  the  successive 
periods  are  represented  in  order,  from  the  Azoic,  in  northern 
New  York,  southwestward  to  the  Coal  formation  of  Penn- 
sylvania, showing  that  they  succeed  one  another  on  the 
map  simply  because  they  come  to  the  surface  in  succession. 
The  amount  of  dip  and  its  regularity  are  greatly  exag- 
gerated in  the  section;  and  there  is  no  attempt  to  give 
the  relative  thickness  of  the  beds. 


I.  AZOIC  TIME,  OR  AGE. 

1.  Rocks:  kinds  and  distribution. 

1.  Distribution. — The  Azoic  Age  commenced  with  tho 
origin  of  the  earth's  crust,  and  includes  the  oldest  rocks  of 
the  globe.  Its  formations  are  those  upon  which  the  fos- 
siliferous  rocks  of  the  Silurian  and  subsequent  ages  have 
been  spread  out,  and  the  material  out  of  which  most  of  these 
later  rocks  have  been  made. 

The  Azoic  rocks  extend  around  the  whole  sphere;  but,  in 
general,  they  are  concealed  from  view  by  subsequent  forma- 
tions. In  North  America  they  are  surface  rocks  over  a  largo 
area  north  of  the  great  lakes,  the  longer  branch  of  which 
area  runs  northwest  to  the  Arctic  Ocean,  and  the  shorter, 
northeast  to  Labrador.  The  white  area  on  the  following 
map,  in  what  is  now  British  America,  is  the  portion  of  tho 
continent  covered  with  Azoic  rocks. 

The  shape  is  a  little  like  that  of  the  letter  V.  There 
is  also  a  small  Azoic  area  in  northern  New  York  (see  map, 
p.  71);  another  south  of  Lake  Superior;  and  a  few  other 
spots  cast  of  the  Rocky  Mountains.  TV  hat  portion  of  tho 
Rocky  Mountain  region,  or  the  country  beyond,  may  be 
Azoic  at  surface,  is  not  known. 


GEOGRAPHICAL   DISTRIBUTION.  73 

In  Europe,  Azoic  rocks  are  in  view  in  the  great  iron 
regions  of  Sweden  and  Norway,  in  Bohemia,  and  in  north- 
ern Scotland. 

2.  Kinds  of  Rocks. — The  rocks  are  mostly  crystalline  rocks, 
Buck  as  granite,  syenite,  gneiss,  hornblendic  gneiss,  mica- 
Fig.  127. 


Azoic  Map  of  North  America. 

schist,  hornblendic,  chloritic,  and  talcose  schists,  and  granu- 
lar limestone.  But  besides  these  there  are  some  hard  con- 
glomerates, quartz-rocks  or  gritty  sandstones,  and  slates. 
The  beautiful  iridescent  feldspar  called  labradorite  is  a 
common  constituent  of  some  of  the  crystalline  or  granitic 
rocks. 

Along  with  the  rocks  there  are,  in  some  regions,  immense 


74 


AZOIC   AGE. 


Pig.  128. 


beds  of  iron  ore  (i,  t,  i  in  fig.  128).      In  northern  New  York 

there  are  beds  100  to  700  feet  thick.  In  Missouri  there  are  two 

"iron  mountains,"  as  they  are  called; 

one,  the  Pilot  Knob,  is  581  feet  high, 

the   other  228  feet.     Similar  iron-ore 

beds  occur  in  Michigan,  south  of  Lake 

Superior. 

3.  Disturbance  and  Crystallization  of  the  Rocks. — The  layers 
of  gneiss  and  other  schistose  rocks,  with  the  included  lime- 
stones, are  nowhere  horizontal;  but,  instead  of  this,  they 
dip  at  all  angles,  and  are  often  flexed  or  folded  in  a  most 
complex  manner.  Fig.  129  represents  the  folded  character 

Fig.  129. 


Kg.  129,  by  Logan,  from  the  south  side  of  the  St.  Lawrence  in  Canada,  between  Cascade 
Point  and  St. Louis  Rapids;  1,  gneiss. 

of  the  Azoic  rocks  of  Canada.  The  folded  rocks  in  this 
figure  are  overlaid  by  beds  that  are  nearly  horizontal,  which 
belong  to  the  Lower  Silurian. 

Owing  to  the  dislocations  and  uplifts  which  the  rocks 
have  undergone,  the  iron-ore  beds  look  like  veins;  and  even 
the  strata  of  crystalline  limestone  have  often  a  similar  vein- 
like  appearance.  "Where  strata  have  been  thrown  up  so  that 
the  layers  stand  vertical,  the  included  bed  of  ore  will  be 
vertical  also,  and  will  descend  downward  in  the  same  man- 
ner as  a  true  metallic  vein ;  and  through  the  breaking  and 
faulting  of  the  strata,  many  of  those  irregularities  would 
result  that  are  so  common  in  veins. 

Gneiss,  mica-schist,  granular  limestone,  and  other  crys- 
talline rocks  have  been  described  on  page  23  as  metamor- 
phic  rocks, — rocks  that  were  once  horizontal  sandstones, 
shales,  and  stratified  limestones,  and  which  have  been, 


DISTURBANCES    OF    BEDS.  75 

by  some  process,  crystallized.  The  gneiss  and  schists  in 
Azoic  regions  are  actually  in  layers  or  strata,  alternating 
with  one  another,  as  common  with  ordinary  sandstones  and 
shales ;  and  the  ore-beds  are  conformable  to  the  layers  of 
schist  and  quartz-rock  in  which  they  occur. 

4.  Conclusions  as  to  the  Origin  of  the  Rocks. — The  following 
conclusions  hence  follow : — (1)  That  the  Azoic  rocks  here 
referred  to  were  originally  horizontal  strata  of  sandstones, 
shales,  and  limestones ;  (2)  That  after  their  formation  they 
were  pushed  out  of  place  by  some  great  movement  of  the 
earth's  crust,  which  uplifted  and  folded  them,  so  that  now 
they  are  nowhere  horizontal;  (3)  That,  besides  being  dis- 
placed, they  were  also  crystallized, — that  is,  changed  into 
metamorphic  rocks.  Even  the  sandstones  and  conglomerates 
of  the  Azoic  give  evidence  by  their  hardness  of  the  action 
of  the  same  heat  that  caused  the  crystallization  of  other 
Azoic  strata. 

It  is  altogether  probable  that  the  time  of  the  uplifting 
and  that  of  the  metamorphism  were  the  same.  There  may 
have  been  many  such  metarmophic  epochs  in  the  course  of 
the  Azoic  age.  But,  since  even  the  latest  beds  of  the  Azoic 
are  thus  upturned  and  crystallized,  an  extensive  revolution 
of  this  kind  must  have  been  a  closing  event  of  the  age.  Fig. 
129  shows  that  the  upturning  preceded  the  formation  of 
the  lowest  Silurian  beds,  for  these  lie  undisturbed  over  the 
folded  and  crystallized  Azoic. 

Below  the  surface  Azoic  rocks,  there  must  be  others,  con- 
stituting the  interior  portions  of  the  earth's  crust.  If  the  earth 
were  originally  a  melted  globe,  as  appears  altogether  pro- 
bable, the  earth's  crust  is  its  cooled  exterior.  Whenever 
the  crust  formed,  its  surface  must  have  been  at  once  worn 
by  the  waves,  wherever  within  their  reach,  and  deposits  of 
sand,  pebbles,  and  clay  must  have  been  formed ;  and  in  this 
way  the  Azoic  formations  were  begun.  But  at  the  same 
time  that  these  surface  strata  were  in  progress,  the  crust 


76  AZOIC   AGE. 

would  have  been  increasing  in  thickness  within  by  the  cool- 
ing which  was  continuing  its  progress.  Of  the  interior  rock 
of  the  crust  we  know  little  or  nothing. 

2.  Life. 

The  Azoic  rocks  as  far  as  they  have  been  examined,  con- 
tain no  fossils.  It  is  not  yet  certain,  however,  that  some 
life  may  not  have  existed  on  the  globe  before  the  close  of 
the  age. 

There  is  abundant  reason  for  concluding  that  if  there  were 
any  plants,  they  were  only  sea-weeds;  for  none  but  sea- weeds 
occur  in  the  overlying  Lower  Silurian  formations.  If  there 
were  any  animal  life,  it  is  probable  that  it  included  only  the 
minute  animalcular  forms;  since  if  shells  and  corals  were  in 
the  seas  their  remains  would  have  been  preserved  in  some 
of  the  beds  that  were  least  altered  by  the  heat  of  meta- 
morphism. 

The  graphite  in  certain  Azoic  rocks,  as  in  those  near 
Ticonderoga,  is  sometimes  thought  to  be  evidence  of  the 
existence  of  plants,  because  it  is  known  that  in  later  times 
graphite  has  been  formed  out  of  the  remains  of  plants.  The 
limestone  beds  have  suggested  the  idea  that  there  may  have 
been  animal  life  of  some  kinds;  for  almost  all  limestones 
(see  p.  21)  are  of  organic  origin.  But  the  evidence  with 
regard  to  both  plants  and  animals  is  still  doubtful. 

3.  General  Observations. 

The  large  Azoic  area  on  the  map,  p.  73,  represents  the 
main  portion  of  the  dry  land  of  North  America  in  the  later 
part  or  at  the  close  of  the  Azoic  age ;  for  it  consists  of  the 
rocks  made  during  the  age,  and  is  bordered,  on  its  different 
sides,  by  the  earliest  rocks  of  the  next  age.  It  is  the  outline, 
approximately,  of  Azoic  North  America,  or  the  continent,  as 
it  appeared  when  the  Silurian  age  opened.  It  is,  therefore, 
the  beginning  of  the  dry  land  of  North  America,  the  original 


GENERAL   OBSERVATIONS.  77 

nucleus  of  the  continent,  to  which  additions  were  made,  in 
succession,  with  the  progress  of  the  ages,  until  its  final  com- 
pletion as  the  age  of  Man  was  opening.  The  smaller  Azoic 
areas  mentioned  appear  to  have  been  mere  islets  in  the 
great  continental  sea. 

Each  of  the  other  continents  was  probably  represented 
at  the  same  time  by  its  spot,  or  spots,  of  dry  land.  All  the 
rest  of  the  sphere,  excepting  these  limited  areas,  was  an 
expanse  of  waters. 

The  evidence  appears  also  to  show  that  both  waters  and 
land  were  lifeless  wastes,  except  it  be  that  sea-weeds  and 
Protozoans  were  in  the  oceans. 

The  facts  to  be  presented  under  the  Silurian  age  teach 
that  the  great,  yet  unmade,  continents,  although  so  small  in 
the  amount  of  dry  land,  were  not  covered  by  the  deep  ocean, 
but  only  by  shallow  oceanic  waters.  They  lay  just  beneath 
the  waves,  already  outlined,  prepared  to  commence  that 
series  of  formations — the  Silurian,  Devonian,  Carboniferous, 
and  others — which  was  required  to  finish  the  crust  for  its 
ultimate  continental  purposes. 

"We  thus  gather  some  hints  with  regard  to  the  geography 
of  America  in  the  period  of  its  first  beginnings.  It  is  stated, 
in  Genesis,  that  on  the  third  day  the  waters  were  gathered 
together  into  one  place,  and  the  dry  land  was  made  to  appear, 
and  also  that,  as  a  second  work  of  the  same  day,  plants  were 
called  into  existence  as  the  first  life  of  the  earth.  The  Azoic 
age  in  geology  witnessed,  with  little  doubt,  the  appearance 
of  the  first  continents  and  probably  of  the  first  plants. 

The  outline  of  the  northern  Azoic  area  on  the  map,  p.  73 
— the  embryo  of  the  continent — is  very  nearly  parallel  to 
that  of  the  present  continent.  The  Azoic  lands,  both  in 
North  America  and  Europe,  are  largest  in  the  more  northern 
latitudes. 


78  PALEOZOIC   TIME. — LOWER   SILURIAN. 


n.  PALEOZOIC  TIME. 

PALEOZOIC  time  includes  three  ages : — 

1.  The  AGE  OF  MOLLUSKS,  or  SILURIAN  AGE. 

2.  The  AGE  OF  FISHES,  or  DEVONIAN  AGE. 

3.  The  AGE  OF  COAL-PLANTS,  or  CARBONIFEROUS  AGE. 

In  describing  the  rocks  of  these  ages  over  North  Ame- 
rica, and  the  events  connected  with  their  history,  there  are 
three  distinct  regions  to  be  noted, — distinct,  because  in  an 
important  degree  independent  in  their  history.  These  are — 

1.  The  Eastern  border  region,  or  that  near  the  Atlantic 
border,  including  central  and  eastern  New  England,  New 
Brunswick  and  Nova  Scotia,  and  the  coast  region  south  of 
New  York. 

2.  The  Appalachian  region,  or  that  now  occupied  by  the 
Appalachian  Mountain  chain,  from  Labrador,  on  the  north, 
along  by  the  Green  Mountains,  and  the  continuation  of  the 
heights  through  New  Jersey,  Pennsylvania,  Virginia,  east- 
ern Tennessee,  and  so  southwestward  to  Alabama. 

3.  The  Interior   Continental   region,  or  that  west  of  the 
Appalachian  region,  continued  over  much  of  the  present 
eastern  slope  of  the  Eocky  Mountain  chain. 

We  may  have  hereafter  to  recognize  a  Rocky  Mountain 
region  and  a  Western  border  region,  and  others  on  the  north ; 
but  at  present  the  geology  of  these  regions  is  too  imperfectly 
known  to  render  it  necessary. 

I.  AGE  OF  MOLLUSKS,  OR  SILURIAN  AGE. 

This  Age  is  called  Silurian,  from  the  region  of  the  ancient 
Silures  in  Wales,  where  the  rocks  occur.  It  was  first  so 
named  by  Murchison. 

The  Age  is  naturally  divided  into  Lower  and  Upper  Silu- 
rian, each  corresponding,  in  America,  to  three  periods,  thus : 


POTSDAM  PERIOD.  79 

1.  LOWER  SILURIAN. 

1.  Potsdam,  or  Primordial  Period. 

2.  Trenton  Period :  Bala  formation  and  Llandeilo  flags  of 
England. 

3.  Hudson  Period :  Lower  Caradoe,  or  Upper  Llandeilo 
beds  of  England. 

2.  UPPER  SILURIAN. 

1.  Niagara  Period :  Wenlock  beds  of  England,  either  in 
part,  or  wholly. 

2.  Salina  Period. 

3.  Lower  Helderberg  Period :  Ludlow  beds  of  England, 
or  all  but  their  upper  portion. 

The  Silurian  is  also  sometimes  divided  as  follows : — 

1.  PRIMORDIAL  SILURIAN,  or  Potsdam  Period.     The  term 
Primordial  signifies  first  in  order,  or,  in  this  place,  the  period 
of  the  first  life  of  the  globe. 

2.  MIDDLE  SILURIAN  ;  corresponding  to  the  remainder  of 
the  Lower  Silurian. 

3.  UPPER  SILURIAN. — The  same  as  above  given. 

'  1.  PRIMORDIAL,  OR  POTSDAM  PERIOD. 

1.  Rocks:  kinds  and  distribution. 

The  strata  of  the  Primordial  or  Potsdam  period,  in  Ame- 
rica, over  the  Interior  Continental  basin,  are  exposed  to  view 
at  intervals  from  New  York  to  the  Mississippi  River;  beyond 
the  river,  over  some  parts  of  the  eastern  slopes  of  the  Rocky 
Mountains;  and  also  in  Texas.  The  area  on  the  map  of  New 
York  and  Canada  (p.  71)  is  that  numbered  2,  lying  next  to 
the  Azoic.  There  is  reason  to  believe,  from  the  many  points 
at  which  the  strata  come  to  the  surface  (as  in  Michigan,  Wis- 
consin, Iowa,  Missouri,  Tennessee,  Texas,  the  Upper  Mis- 
souri region),  that  they  extend  over  the  larger  part  of  the 
continent  outside  of  the  Azoic  area  represented  on  the  map, 


80  PALEOZOIC   TIME — LOWER   SILURIAN. 

p.  73,  though  concealed  by  other  less  ancient  strata  over 
most  of  the  surface. 

Through  this  interior  region  the  lower  rocks  are  mainly 
a  sandstone, — called  the  Potsdam  sandstone,  from  a  locality 
in  northern  New  York.  The  sandstone  beds  contain,  in 
many  places,  ripple-marks  (fig.  18,  p.  32) ;  mud-cracks  (fig. 
20) ;  layers  showing  the  wind-drift  and  ebb-and-flow  struc- 
ture (figs.  17/,  e,);  worm-burrows,  and  also  occasionally  the 
tracks  of  some  of  the  animals  of  the  period.  The  upper 
rocks  in  New  York,  and  in  the  same  latitudes  west,  are 
sandstone,  containing  some  carbonate  of  lime,  and  called  the 
Calciferous  beds;  but  more  to  the  south  in  the  Mississippi 
Valley  the  beds  are  mainly  a  magnesian  limestone,  called 
the  Lower  Magnesian. 

In  the  Appalachian  region  in  Vermont,  north  in  Canada, 
and  in  Pennsylvania,  etc.,  the  rocks  are  slates  overlying 
sandstone,— the  whole  2000  to  7000  feet  or  more  thick, 
exceeding  many  times  the  thickness  to  the  west.  In  the 
Eastern  border  region  beds  of  the  period  occur  at  Braintree 
near  Boston,  and  near  the  Labrador  coast. 

In  Great  Britain  the  primordial  rocks  are  hard  sandstones 
and  slates,  called  in  part  the  Lingula  flags.  They  are  most 
extensively  in  view  in  north  and  south  Wales  and  in  Shrop- 
shire. A  lower  portion  of  the  series,  of  great  thickness, 
consisting  of  slates  and  other  rocks,  has  been  named  Cam- 
brian by  Sedgwick. 

In  Lapland,  Norway,  Sweden,  and  Bohemia,  Primordial 
strata  have  been  observed.  If  the  strata  of  later  date  could 
be  removed  from  the  continents,  we  should  probably  find  the 
primordial  beds  extensively  distributed  over  all  the  conti- 
nents. 

2.  Life. 

These  most  ancient  of  fossiliferous  rocks  contain  no 
remains  of  terrestrial  life.  The  plants  of  the  period  were  all 
sea-weed*.  Among  animals,  the  sub-kingdoms  of  Radiates, 


POTSDAM    PERIOD.  81 

Mollusks,  and  Articulates  were  represented  by  water-species, 
and  by  these  alone.  There  is  no  evidence  that  there  were 
any  Vertebrates. 

The  older  sandstone  abounds  in  many  places  in  a  shell 
smaller,  in  general,  than  a  finger-nail,  called  a  Lingula  (fig. 
133).  It  is  the  shell  of  a  Mollusk  of  the  tribe  of  Brachiopods. 
It  stood  on  a  stem,  when  alive,  as  represented  in  fig.  82,  p. 
55.  These  shells  are  so  characteristic  of  the  beds  in  many 


Fig.  130,  Phyllograptus  Typus;  131,  132,  Graptolithus  Loganl;  133,  Lingula  prima;  134, 
Ophileta  levata;  135,  Leperditia  Anna;  136,  same,  natural  size;  137,  Paradoxides  Harlaol 
(X%);  138,  Track  of  a  Trilobite  (X  %)• 

regions  as  to  give  them  the  name  of  Lingula  flags,  or  Lin- 
gula sandstone. 


82  PALEOZOIC   TIME — LOWER    SILURIAN. 

Another  tribe  very  prominent  among  the  earliest  of  tho 
earth's  animals  is  that  of  Trilobites,  of  the  sub-kingdom  of 
Articulates,  and  class  of  Crustaceans. 

One  of  the  largest  species  of  them  is  represented  in  fig 
137,  reduced  to  one-sixth  the  natural  length.  Its  total 
length,  when  living,  must  have  been  18  inches  or  more,  and 
hence  it  was  as  large  as  any  living  Crustacean.  The  speci- 
men figured  was  found  at  Braintrce  south  of  Boston.  It  is 
Keen  to  have  had  large  eyes  situated  on  the  head-shield, — 
evidence,  as  Buckland  observed,  of  the  clear  waters  and 
clear  skies  of  Primordial  time.  As  no  legs  are  ever  found 
in  connection  with  Trilobites,  they  are  supposed  to  have 
had  only  thin  membranous  or  foliaceous  plates  for  swimming. 
Fig.  138  shows  the  track  of  a  large  animal  found  by  Logan 
in  the  Canada  beds  (and  reduced  like  fig.  137),  which  may 
have  been  made  by  one  of  the  great  Trilobites  as  it  crawled 
over  the  sand. 

Another  group,  characterizing  especially  the  later  half  of 
the  period,  is  that  of  Graptolites,  two  specimens  of  which  are 
shown  in  figs.  130,  131,  and  an  enlarged  view  of  part  of  fig. 
131  in  fig.  132.  The  species  are  so  named  from  the  Greek 
grapho,  I  write,  in  allusion  to  their  having  commonly  a  plume- 
like  form.  The  fossils  are  very  thin,  and  are  supposed  to  have 
consisted  of  the  cells  of  minute  Radiate  animals,  allied  to  the 
Hydroid  Acalephs  (p.  5S).  A  great  number  of  species  have 
been  described.  They  appear  to  have  grown  like  delicate 
mossy  plants  densely  over  the  muddy  bottom  of  the  sea. 

Among  Mollusks,  besides  Braehiopods,  there  were  also 
Gasteropods,  one  of  which  is  shown  in  fig.  134. 

Crustaceans  were  represented  also  by  a  few  species  a  little 
like  shrimps  in  general  form,  but  having  foliaceous  legs  like 
the  Trilobites,  and  called  Phyllopods;  also  by  Ostracoids,  one 
species  of  which  is  shown,  enlarged,  in  fig.  135,  and  of  natu- 
ral size  in  fig.  136.  These  little  Ostracoids,  though  insig- 


POTSDAM   PERIOD.  83 

nificant  in  size,  are  so  abundant  in  some  places  as  nearly  to 
make  up  the  mass  of  a  slate. 

The  existence  of  marine  worms  among  the  earliest  animals 
of  the  globe,  is  proved  by  the  great  numbers  of  worm-holes 
or  burrows  in  the  sandstones,  now  filled  with  the  hard  sand- 
stone like  that  of  the  rock.  They  are  very  similar  to  the 
holes  made  by  such  worms  in  the  sands  of  sea-shores  at  the 
present  time.  One  species  is  called  Scolithus  linearis.  These 
worm-holes  are  common  in  the  European  as  well  as  Ame- 
rican Primordial  sandstones. 

There  were  also  'Crinoids  of  the  sub-kingdom  of  Eadiates 
(p.  58),  for  disks  from  the  broken  stems  of  Crinoids  are  not 
uncommon.  And  among  Protozoans  there  were  at  least 
Sponges,  if  not  also  the  minute  Rhizopods  and  Polycystines 
(p.  59). 

Sponges  among  Protozoans, — Graptolites  and  Crinoids 
among  Radiates, — Brachiopods  and  some  representatives  of 
other  tribes  among  Mollusks, — Worms  and  Trilobites,  and  a 
few  other  Crustaceans,  among  Articulates, — and  Sea-weeds 
among  Plants, — made  up  the  living  species;  and  in  this  Prim- 
ordial population,  Trilobites  took  the  lead.  There  is  as  yet 
no  evidence  that  the  dry  Primordial  hills  bore  a  moss  or 
lichen,  or  harbored  the  meanest  insect,  or  that  the  oceans 
contained  a  single  fish. 

3.  General  Observations. 

The  ripple-marks,  mud-cracks,  and  tracks  of  animals  pre- 
served in  this  most  ancient  of  Paleozoic  rocks  are  records 
left  by  the  waves,  the  sun,  and  the  life  of  the  period,  as  to 
the  extent  and  condition  of  the  continent  in  that  early  era ; 
and  the  layers  having  the  wind-drift  structure  or  the  ebb- 
and-flow  structure  are  other  evidence  of  similar  import. 
These  markings  teach  that  when  the  beds  were  in  progress 
a  large  part  of  the  continent  lay  at  shallow  depths  in  the 
eea,  so  shallow  that  the  waves  could  ripple  its  sands; — that 


84  PALEOZOIC   TIME — LOWER   SILURIAN. 

over  other  portions  the  surface  was  a  sand-flat  exposed  at 
low  tide;  or  a  sea-beach,  the  burro  wing-place  of  worms; — 
or  a  mud-flat,  that  could  be  dried  and  cracked  under  the 
heat  of  the  sun,  or  in  a  drying  atmosphere;  or  a  field 
of  drift  heaps  of  sands,  beyond  the  reach  of  the  tides,  which 
the  winds,  now  gentle  in  movement,  and  now  blowing  in 
gales,  had  gradually  built  up. 

With  such  evidences  of  shallow  water  or  emerged  sand 
in  a  formation  extending  widely  over  the  continent,  it  is  a 
safe  conclusion  that  the  North  American  continent  was 
at  the  time  in  actual  existence,  and  probably  not  far  from 
its  present  extent ;  and,  although  partly  below  the  sea-level, 
it  was  generally  at  shallow  depths.  The  same  may  prove 
to  have  been  true  of  the  other  continents.  There  is,  in  fact, 
evidence  of  other  kinds  which,  taken  in  connection  with  the 
above,  leaves  little  doubt  that  the  existing  places  of  the  deep 
ocean  and  of  the  continents  were  determined  even  in  the 
first  formation  of  the  earth's  crust  in  the  early  Azoic,  and 
that,  in  all  the  movements  that  have  since  occurred,  the 
oceans  and  continents  have  never  changed  places. 

This  preservation  of  markings,  seemingly  so  perishable, 
on  the  early  shifting  sands,  is  a  very  instructive  fact.  They 
illustrate  part  of  the  means  by  which  the  earth  has,  through 
time,  been  recording  its  own  history.  The  track  of  a  Trilo- 
bite  or  of  a  wavelet  is  a  mould  in  sand  or  earth,  into  which 
other  sands  are  cast  both  to  copy  and  preserve  it ;  for  if  the 
waves  or  currents  that  succeed  are  light,  they  simply  spread 
new  sands  over  the  indented  surface,  without  obliterating 
the  mould;  and  so  the  addition  of  successive  layers  only 
buries  the  markings  more  deeply  and  thus  protects  them 
against  destruction.  When,  finally,  consolidation  takes 
place,  the  track  or  ripple-mark  is  made  as  enduring  as  the 
rock  itself. 

After  the  formation  in  North  America  of  the  great  Primor- 
dial sandstone,  there  was  a  change  in  the  condition  of  the 


TRENTON    AND    HUDSON    PERIODS.  85 

•surface,  t  specially  over  the  interior  of  the  continent.  For 
limestone  strata  began  then  to  form  where  sandstones  were 
in  progress  before.  This  change  was  probably  some  increase 
in  the  depth  and  clearness  of  the  interior  of  the  continental 
sea.  Along  the  borders  of  this  sea — that  is,  in  New  York 
and  along  the  Appalachian  region  from  Quebec  into  Vir- 
ginia— the  rock  was  still  a  sandstone  or  shale,  though  often 
more  or  less  calcareous  in  its  composition. 

The  limestone  of  the  interior  region  is  remarkably  free 
from  fossils ;  and  if,  as  is  probable,  it  was  of  organic  origin, 
it  follows  either  that  the  fossils  were  all  ground  to  powder 
to  make  the  rock,  or  else  they  were  too  minute  to  need 
grinding, — like  the  Ehizopods  figured  on  page  59,  which 
seldom  exceed  the  finest  grains  of  sand  in  size.  Now,  since 
such  Ehizopods  made  the  strata  of  chalk  at  a  later  age,  and 
since  also  they  constitute  at  the  present  time  the  bed  of  the 
ocean  over  immense  areas  in  both  deep  and  shallow  waters, 
and  inasmuch  as  their  existence  in  the  Lower  Silurian  era 
has  been  proved  by  finding  fossils  of  them  (though  not  in 
the  rock  here  under  consideration),  it  is  certainly  possible 
that  the  magnesian  limestones  of  the  period  may  have  been 
formed  out  of  the  remains  of  Ehizopods. 

Whether  the  reasoning  here  used  be  regarded  as  satisfac- 
tory or  not,  the  above  will  serve  to  illustrate  the  methods 
of  searching  into  the  geography  of  the  ancient  world  that 
are  within  the  reach  of  the  geologist.  And  when  the  facts 
are  all  fully  known,  there  is  little  reason  to  doubt  that  the 
results  arrived  at  will  be  in  the  main  right. 

2.  TRENTON  AND  HUDSON  PERIODS. 

The  Middle  Silurian  includes  the  Trenton  and  Hudson 
periods  of  America,  and  those  of  the  Bala  limestone  and 
Llandeilo  flags  of  Great  Britain. 


86  PALEOZOIC   TIME — LOWER   SILURIAN. 

Rocks:  kinds  and  distribution. 

In  the  Primordial  period  of  America,  there  was,  first,  the 
spreading  out  of  a  great  sandstone  over  the  submerged  por 
tions  of  the  continent ;  afterwards,  the  formation  of  a  lime- 
stone about  the  middle  of  the  Interior  Continental  basin, 
while  sandstones  but  little  calcareous  were  forming  along 
the  northern  United  States  and  over  the  Appalachian 
region. 

In  the  next  period,  called  the  Trenton,  limestones  were 
in  progress  over  the  Appalachian  region,  as  well  as  a  very 
large  part  of  the  Interior  Continental  basin, — northeastern, 
northern,  and  southern.  It  was  the  most  universal  of  all 
limestone  formations.  It  is  numbered  3  on  the  map,  p.  71. 

The  rock  differs  from  the  Lower  Magnesian  limestone  in 
being  full  of  fossils, — shells,  crinoidal  remains,  corals,  etc. ; 
and  often  the  fossil  shells  and  corals  are  so  crowded  together 
that  no  spot  as  large  as  the  end  of  the  finger  can  be  found 
without  one  or  more  of  them.  In  fact,  if  the  portions  which 
seem  to  be  without  them  are  sliced  very  thin  and  examined 
under  a  microscope,  they  are  found  to  be  made  up  of  frag- 
ments of  fossils. 

The  thickness  of  these  rocks  in  some  portions  of  the  Ap- 
palachian region  is  6000  to  8000  feet,  or  more  than  ten  times 
the  thickness  in  the  larger  part  of  the  Interior  Continental 
region. 

The  name  Trenton  is  derived  from  Trenton  Falls,  north 
of  Utica,  New  York,  where  the  Trenton  limestone  is  exposed 
in  high  bluffs  along  the  banks  of  the  stream.  The  "  Chazy," 
"  Birdseye,"  and  "  Black  Elver"  limestones  are  the  lower 
strata,  in  succession,  of  the  Trenton  Period,  the  Chazy  being 
the  oldest. 

In  the  Green  Mountains  these  limestones  are  now  in  the 
condition  of  white  statuary  or  building  marble;  for  they 
are  the  marbles  of  the  Stockbridge  and  other  quarries  in 


TRENTON   AND    HUDSON   PERIODS.  87 

Berkshire,  Massachusetts,  and  of  those  of  Vermont.  They 
have  been  altered  or  metamorphosed,  in  this  part  of  the 
Appalachian  region,  into  a  crystalline  rock,  or,  in  other 
words,  they  are  metamorphic  limestones  (see  p.  21).  In  the 
process  of  change  they  have  lost  all  their  fossils,  excepting 
a  rare  example,  as  at  Sudbury,  Vermont.  Other  associated 
rocks  in  the  same  region  are  also  metamorphic,  or  more  or 
less  crystalline. 

Before  the  close  of  the  Lower  Silurian — that  is,  in  the 
Hudson  period — the  area  of  limestone-making  had  again 
contracted.  Over  the  Appalachian  region  in  Pennsylvania, 
and  in  the  northern  portion  of  the  Interior  Continental  region, 
— that  is,  through  New  York  State  and  the  same  latitudes 
to  the  westward, — the  rocks  are  shales  and  shaly  sandstones; 
while  in  Ohio  and  some  other  States  beyond  they  consist  of 
shales  and  limestones,  or  shaly  limestones.  The  Utica  shale 
and  Lorraine  shale  of  central  New  York  are  of  this  period 
(see  No.  4,  on  the  map,  p.  71). 

The  rocks  of  the  Middle  Silurian,  in  Great  Britain,  are 
shales  and  shaly  sandstones,  with  but  little  limestone.  The 
Llandeilo  flags  are  shaly  sandstones;  and,  together  with  the 
associated  shales,  they  have  a  thickness  of  many  thousand 
feet.  Above  them  there  are  the  Caradoc  sandstone  of  Shrop- 
shire and  the  Bala  formation — the  latter  including  some 
limestone  in  Wales.  In  Scandinavia  there  are  limestone 
formations,  overlaid  by  slates  and  flags;  in  Eussia  and  the 
Baltic  provinces — part  of  the  Interior  Continental  portion 
of  the  Eastern  Continent — the  rocks  are  mainly  limestones. 

2.  Life. 

The  life  of  the  Middle  Silurian,  like  that  of  the  Primordial 
period,  was,  as  far  as  evidence  has  been  collected  from  the 
American  or  foreign  rocks,  wholly  marine :  no  trace  of  a 
terrestrial  or  fresh-water  species  of  plant  or  animal  has 
been  found. 


88  PALEOZOIC    TIME SILURIAN. 

The  plants  were  sea-weeds  alone. 

All  the  sub-kingdoms  of  animals  were  represented,  with  the 
exception  of  the  Vertebrates.  Among  Radiates  there  were  Corals 
and  Crinoids;  among  Mollusks,  representatives  of  all  tho 
several  orders;  among  Articulates,  the  Avater-divisions, 
Worms  and  Crustaceans. 

1.  Radiates. — Fig.  139  represents  one  of  the  Corals.     Its 
shape  is  that  of  a  curved  cone,  a  little  like  a  short  horn,  the 
email  end  being  the  lower.     At  top,  when  perfect,  there  is 
a  cavity  divided  off  by  plates  radiating  from  the  centre. 
Such  corals  are  called  Cyathophylloid  corals,  from  the  Greek 
kuathos,  cup,  and  phullon,  leaf,  alluding  to  the  cup  full  of 
radiating  leaves  or  plates.    When  living,  the  coral  occupied 
the  interior  of  an  animal  similar  to  that  represented  in  fig. 
91  or  95. 

Another  kind  of  coral,  of  a  hemispherical  form,  and  made 
up  of  very  fine  columns,  is  represented  in  figs.  140,  141,  the 
latter  showing  the  interior  appearance.  It  is  called  Chcctetes 
Lycoperdon.  Another,  of  coarser  columns, — each  nearly  a 
sixth  of  an  inch  in  diameter, — is  called  the  Columnaria  alveo- 
lata.  In  a  transverse  section  tho  columns  are  divided  off  by 
horizontal  partitions.  Masses  of  this  coral  have  been  found 
which  weigh  each  between  two  and  three  thousand  pounds.' 

Fig.  142  shows  the  form  of  one  of  the  Crinoids,  though 
the  stem  on  which  it  stood  is  mostly  wanting,  and  the  arms 
are  not  entire.  The  mouth  was  in  the  centre  above,  and  the 
animal  was  like  a  star-fish  with  branching  arms,  turned 
bottom-upward,  and  standing  on  a  jointed  stem.  There 
were  also  true  star-fishes  in  the  seas. 

2.  Jfollusks. — Among  jfrfollusks,  Bryozoans  were  very  com. 
mon :  the  fossils  are  small  cellular  corals :  one  is  shown  in 
fig.  143,  and  a  portion,  enlarged,  in  fig.  144.      Brachiopods 
were  still  more  characteristic  of  the  period,  and  occur  in 
vast  numbers.     Fig.  145  is  0.  testudinaria ;  fig.  146,  0.  occi- 
dentalis;  fig.  147,  Leptcena  sericea.     There  were  also  some 


TRENTON    AND    HUDSON    PERIODS. 


89 


Conchifcrs,  as  fig.  148,  Avicula?  Trentonensis ;    and   some 
Gasteropods,  as  fig.  149,  Pleurotomaria  lenticularis.     Shells 


Fig.  139-151. 


RADIATES. — Fig.  139,  Potraia  Cornicnlnm;  140, 141,  Chsetetes  Lycoperdon;  142,  Lecanocriims 
elegans.— MOLLUSKS  :  Figs.  143, 144,  Ptilodictya  fenestrat?  ;  145,  Orthis  testudinaria;  146, 
Orthis  occidentalis ;  147,  Leptsena  sericea ;  148,  Avicula  (?)  Trentonensis ;  149,  Pleurotomaria 
lenticularis;  150,0rthoceras  junceum.— ARTICULATES:  Fig.  151,  Asaphus  (Isotelus)  gigas. 

of  Cephalopods  were  especially  common  under  the  form  of 
a  straight  or  curved  horn  with  transverse  partitions.  Fig. 
150,  Orthoceras  junceum,  represents  a  small  species.  One 
kind  had  a  shell  12  or  15  feet  long  and  nearly  a  foot  in 
diameter.  The  word  Orthoceras  is  from  the  Greek  orthos, 
straight,  and  keras,  horn. 

There  were  some  species  also  of  the  genus  Nautilus. 

3.  Articulates. — Fig.  151  represents  one  of  the  large  Trilo- 
bites  of  the  Trenton  rocks,  the  Asaphus  gigas, — a  species 


90  PALEOZOIC    TIME. 

sometimes  found  a  foot  long.  Another  Trilobite  is  the  Caly- 
mene  Blumenbachii,  of  Europe,  represented  in  fig.  73,  p.  54, 
very  similar  to  the  C.  senaria  of  the  American  rocks. 

While  Trilobites  appear  to  have  been  the  largest  and 
highest  life  of  the  Primordial  seas,  Cephalopods,  of  the 
Orthoceras  family,  far  exceeded  Trilobites  in  both  respects 
in  the  Trenton  period.  The  larger  kinds  must  have  been 
powerful  animals  to  have  borne  and  wielded  a  shell  12 
or  15  feet  long.  Although  clumsy  compared  with  the  fishes 
of  a  later  age,  they  emulated  the  largest  of  fishes  in  size,  and 
no  doubt  also  in  their  voracious  habits.  Crustaceans,  in  their 
highest  divisions,  as  the  Crabs,  may  perhaps  be  regarded 
by  some  as  of  superior  rank  to  Cephalopods.  But  Trilobites, 
of  the  inferior  division  of  Crustaceans,  without  proper 
legs,  living  a  sluggish  life  in  slow  movement  over  the  sands 
or  through  the  shallow  waters,  or  skulking  in  holes,  or 
attached  like  limpets  to  the  rocks,  were  far  inferior  species 
to  the  Cephalopods. 

3.  General  Observations. 

1.  Geography. — The  wide  continental  region  covered  in 
the  Trenton  period  by  the  Trenton  limestone  formation 
stretching  over  the  Appalachian  region  on  the  east,  and 
widely  through  the  Interior  basin,  must  have  been  through- 
out a  clear  sea,  densely  populated  over  its  bottom  with 
Brachiopods,  Corals,  Crinoids,  Trilobites,  and  the  other  life 
of  the  era.  It  may,  however,  have  been  a  shallow  sea ;  for 
the  corals  and  beautiful  shells  of  coral  reefs  live  mostly 
within  100  feet  of  the  surface. 

During  the  next,  or  Hudson  period,  the  same  seas,  espe- 
cially on  the  north,  became  less  free  from  sediment,  through 
some  change  of  level  or  of  coast-barriers,  and  consequently 
much  of  the  former  life  disappeared,  and  other  kinds  sup- 
plied their  places,  adapted  to  impure  waters  or  to  muddy 
bottoms. 


LOWER    SILURIAN.  91 

2.  Disturbances  during  the  Lower  Silurian,  and  at  its  Close. — 
(1.)  Igneous  ejections  in  the  Lake  Superior  district. — Before 
the  close  of  the  Primordial  period  there  were  extensive 
igneous  ejections  through  fractures  of  the  earth's  crust 
in  the  vicinity  of  Lake  Superior,  about  Keweenaw  Point 
and  elsewhere,  and  probably  to  some  extent  also  over 
the  bottom  or  area  of  the  lake  itself,  for  this  is  indi- 
cated by  the  dikes  and  columnar  trap  of  Isle  Royale,  an 
island  in  the  lake.  These  rocks,  which  wrere  melted  when 
ejected,  now  stand,  in  many  places,  in  bold  bluffs  and  ridges; 
and  mixtures  of  scoria  and  sand  make  up  some  of  the  con- 
glomerate beds  of  the  region.  The  sandstones,  penetrated 
by  the  dikes  of  trap,  and  made  partly  before  and  partly  after 
the  ejection,  have  a  thickness  in  some  places  of  six  or  eight 
thousand  feet.  There  appears  to  have  been  a  sinking  of  the 
region  equal  to  the  thickness  of  the  beds,  in  addition  to  the 
igneous  ejections.  The  great  veins  of  native  copper  of  the 
Lake  Superior  region  are  part  of  the  results  of  this  period 
of  disturbance. 

(2.)  Emergence  of  the  region  of  the  Green  Mountains. — The 
changes  from  deep  to  shallow  seas,  or  partly  emerged  flats, 
during  the  Silurian  era,  are  evidence  that  changes  of  level, 
by  gentle  movements  or  oscillations  in  the  earth's  crust, 
were  going  on  throughout  it.  But  after  the  Lower  Silurian 
had  closed,  or  toward  its  close,  there  appear  to  have  been 
greater  and  more  permanent  changes.  The  valley  of  Lake 
Champlain  and  the  Hudson,  as  shown  by  Logan,  probably 
dates  from  this  time.  The  Green  Mountains,  though  not 
raised  to  their  full  height,  then  became  stable  dry  land,  like 
the  Azoic  regions  on  the  map,  p.  73.  That  they  were  not 
dry  land  before,  is  shown  by  the  Trenton  limestones  in  their 
structure,  for  these  are  of  marine  origin ;  and  that  their 
western  side  and  summit  were  above  the  water  from  and 
after  this  time,  is  indicated  by  the  fact  that  the  formations 
of  the  Middle  Silurian  are  the  latest  that  were  there  formed. 
9 


&5  PALEOZOIC   TIME. 

Upper  Silurian  and  Devonian  rocks  exist  over  New  Eng- 
land on  the  east,  and  over  much  of  the  State  of  New  York 
on  the  west  (see  map,  p.  71),  but  not  about  the  top  or 
western  side  of  this  range. 

The  Green  Mountains  appear,  therefore,  to  have  been  the 
portion  of  the  great  Appalachian  chain  which  first  became 
stable  land. 

The  vast  thickness  of  the  several  Lower  Silurian  forma- 
tions along  the  course  of  the  Appalachian  chain,  as  men- 
tioned on  pages  80,  86,  and  the  contrast  in  this  respeet  with 
the  Interior  Continental  region,  are  indications  that  prepa- 
ration was  making  throughout  the  Appalachian  region  which 
were  to  result  ultimately  in  mountains :  the  raising  of  part 
of  the  Green  Mountains  above  the  sea-level,  though  it  may 
have  been  but  to  a  very  small  height,  was  the  commence- 
ment of  the  elevation  of  the  Appalachian  chain. 

3.  Life. — (1.)  Progress. — There  is  no  evidence  that  the 
system  of  life  in  its  progress  during  the  Primordial  and 
Middle  Silurian  had  so  far  advanced  as  to  include  a  terres- 
trial species,  or  the  lowest  of  Vertebrates.  Trilobites  held 
the  first  position  in  the  former  of  these  eras,  Orthocerata 
and  other  Cephalopods  in  the  latter. 

It  was  the  Age  of  Mollusks  ;  and  while  Cephalopods  took 
the  lead  in  the  life  of  the  world,  all  the  other  orders  of  Mol- 
lusks had  their  representatives.  No  other  sub-kingdom  was 
as  well  displayed  in  its  several  grand  divisions,  not  even  that 
of  the  Eadiates.  Among  Articulates,  there  were  neither 
Myriapods,  Spiders,  nor  Insects;  for  these  are  essentially 
terrestrial  animals,  and  the  first  species  of  them  thus  far 
discovered  are  of  the  Devonian  age. 

(2.)  Exterminations  and  Creations. — Among  the  genera  of 
the  Lower  Silurian,  only  five  have  living  species.  These 
are  Isingula,  Discina,  Rhynchondla,  and  Crania  among 
Brachiopods,  and  Nautilus  among  Cephalopods.  These 
genera  of  long  lineage  thus  reach  through  all  time  from 


LOWER   SILURIAN.  93 

the  beginning  of  the  systems  of  life.  All  other  genera 
disappear, — some  at  the  close  of  the  Primordial,  others  at 
that  of  the  Trenton  or  Hudson  period,  or  even  at  the 
termination  of  subordinate  epochs  within  these  periods. 

The  extermination  of  species  .took  place  at  intervals 
through  the  periods,  as  well  as  at  their  close;  though  the 
latter  were  most  universal.  With  the  changes  from  one 
stratum  to  another  there  were  disappearances  of  some 
species,  and  with  the  changes  from  one  formation  to 
another,  still  larger  proportions  became  extinct.  No  Prim- 
ordial species  are  known  to  occur  in  the  Trenton  period; 
very  few  of  the  species  of  the  earlier  epoch  of  the  Trenton 
survive  into  the  next  epoch ;  and  very  many  of  those  of  the 
Trenton  did  not  exist  in  the  Hudson  period.  Thus  life  and 
death  were  in  progress  together,  species  being  removed,  ana 
other  species  being  created,  as  time  moved  on. 

In  the  first  chapter  of  Genesis  we  read  that  on  the  fifth 
day  the  waters  brought  forth  abundantly  the  moving  creatur^ 
that  hath  life;  and  the  rocks  declare  most  decisively  that 
the  waters  were  filled  with  life  when  the  Silurian  age 
opened, — although  but  the  earlier  species  of  the  life  of  that 
fifth  day.  The  eyes  of  the  Trilobites  have  been  referred  to 
as  evidence  of  sunshine  and  clear  skies  in  that  early  era. 
The  existence  of  so  much  animal  life  is  itself  as  good  proof 
of  the  fact ;  for  without  the  sun  the  systems  of  life  could 
not  have  had  even  the  display  they  presented  in  the  Primor- 
dial period.  It  is  clear,  therefore,  that  although  the  first 
vegetation  may  have  existed  in  Azoic  time,  while  the  seas 
were  unduly  warm  and  while,  therefore,  the  earth  was 
densely  shrouded  in  clouds,  as  the  Zoic  ages  began  the 
clouds  were  already  broken,  and  the  earth  had  completed  its 
garniture  of  sky  and  "  greater  and  lesser  lights." 


94  PALEOZOIC    TIME. 

3.  UPPER  SILURIAN  ERA. 

1.  Subdivisions. 

The  Upper  Silurian  in  North  America  includes  three 
periods  :  the  NIAGARA,  the  SALINA,  and  the  LOWER  HELDER- 
BERG.  The  name  of  the  first  is  from  the  Niagara  Kiver, 
along  \vhich  the  rocks  are  displayed;  that  of  the  second, 
from  Salina  in  central  New  York,  the  beds  being  the  salt- 
bearing  rocks  of  that  part  of  the  State ;  that  of  the  third, 
from  the  Helderberg  Mountains,  south  of  Albany,  where 
the  lower  rocks  are  of  this  period. 

2.  Rocks:  kinds  and  distribution. 

The  rocks  of  the  Niagara  period  are — 1,  a  conglomerate 
and  grit-rock  called  the  Oneida  conglomerate,  which  extends 
from  central  Xew  York  southward  along  the  Appalachian 
region,  having  a  thickness  of  700  feet  in  some  parts  of 
Pennsylvania;  2,  shaly  sandstones  of  the  Medina  group, 
which  spread  westward  from  central  ( New  York  through 
Michigan,  and  also  southward  along  the  Appalachian  region, 
being  1500  feet  thick  in  Pennsylvania;  3,  hard  sandstones, 
or  flags  and  shales  of  the  Clinton  group,  having  nearly  the 
same  distribution  as  the  Medina  formation,  though  a  little 
more  widely  spread  in  the  west,  and  about  2000  feet  thick 
in  Pennsylvania ;  4,  the  Niagara  group,  occurring  in  western 
New  York,  and  extending  widely  over  both  the  Appalachian 
and  Interior  Continental  regions ;  it  consists  of  shales  below 
and  thick  limestone  above  at  Niagara,  mainly  of  limestone 
in  the  Interior  region,  and  of  clayey  sandstone  or  shales  in 
the  Appalachian  region,  where  it  has  a  thickness  of  1500 
feet  or  more.  The  Niagara  is  one  of  the  great  limestone 
formations  of  the  continent,  existing  also  in  the  Arctic 
regions. 

Ripple-marks  and  mud-cracks  are  very  common  in  the 


UPPER   SILURIAN.  95 

Medina  formation.  The  example  of  rill-marks  figured  OB 
page  32  is  from  its  strata  in  western  New  York. 

The  Salina  rocks  are  fragile  clayey  sandstones,  marlites, 
and  shales,  usually  reddish  in  color,  and  including  a  little 
limestone.  They  occur  in  New  York  and  sparingly  to  the 
westward,  being  thickest  (700  to  1000  feet  thick)  in  Onon- 
daga  county,  N.Y. 

The  salt  of  Salina  and  Syracuse,  in  central  New  York,  is 
obtained  from  wells  of  salt  water  150  to  310  feet  deep,  which 
are  borings  into  these  saliferous  rocks.  35  to  45  gallons  of 
the  water  afford  a  bushel  of  salt,  while  of  sea-water  it  takes 
350  gallons  for  the  same  amount.  No  salt  is  found  in  solid 
masses.  Gypsum  is  common  in  some  of  the  beds.  A  lime- 
stone called  the  Guelph  formation  overlies  the  Niagara  beds 
at  Guelph  and  in  some  other  parts  of  western  Canada. 

The  Lower  Helderberg  group  consists  mainly  of  limestones, 
and  is  the  second  limestone  formation  of  the  Upper  Silurian. 
But  the  rock  is  generally  impure  or  earthy,  and  the  forma- 
tion is  mostly  confined  to  the  State  of  New  York  and  to  the 
Appalachian  region  on  the  south. 

The  section,  fig.  152,  represents  the  rocks  on  the  Niagara 
Eiver  at  and  below  the  Falls.  The  falls  are  at  F;  the  whirl- 
pool, 3  miles  below,  at  "W;  and  the  Lewiston  Heights,  which 
front  Lake  Ontario,  at  L.  Nos.  1,  2,  3,  4  are  different  sand- 
Fig.  152. 


w 

Section  along  the  Niagara,  from  the  Falls  to  Lewiston  Heights. 

Btone  strata  belonging  to  the  Medina  group;  5,  shale,  and 
6,  limestone,  to  the  Clinton  group;    7,  shale,  and  8,  lime- 


96  PALEOZOIC   TIME 

Btonc,  to  the  Niagara  group.  (Hall.)  The  next  section  (fig. 
153),  from  the  region  south  of  the  eastern  part  of  Lake 
Ontario,  consists  as  follows : — 5  6,  Medina  group,  5  c,  Clinton 

Fig.  153. 


56  be  f>d  6 

Section  of  the  Salina  and  underlying  strata,  from  north  to  south,  south  of  Lake  Ontario. 

group,  5  d,  Niagara  group  (shale  and  limestone),  6,  Salina 
beds.     (Hall.) 

In  Great  Britain,  the  Upper  Silurian  rocks  are  first  sand^ 
stones  and  shales,  called,  when  occurring  in  South  Wales, 
Llandovery  beds,  and  corresponding  to  the  Medina  and  Clin- 
ton groups;  above  these,  the  Wenlock  limestone  group,  con- 
sisting of  limestone  and  some  shale  (and  including  in  the 
upper  portion  the  Dudley  limestone).  These  rocks  occur  as 
surface-rocks  near  the  borders  of  Wales  and  England.  Next 
comes  the  Ludlow  group,  of  the  age  of  the  Lower  Helder- 
berg,  and  perhaps  also  of  the  first  part  of  the  American 
Devonian. 

In  Scandinavia,  the  Gothland  limestone  is  the  equivalent 
of  the  Niagara. 

3.  Life. 

The  limestone  strata  and  most  of  the  other  beds  of  the 
Niagara  group  are  full  of  fossils;  so  also  are  the  rocks 
of  the  Lower  Helderberg  period,  and  the  Wenlock  and 
Ludlow  formations  of  Great  Britain.  The  Salina  formation 
is  almost  wholly  destitute  of  them. 

The  life  of  the  era  was  the  same  in  general  features  as 
that  of  the  later  half  of  the  Lower  Silurian.  It  was  wholly 
marine. 

The  only  plants  were  Algce,  or  sea-weeds. 

In  the  Animal  Kingdom  the  sub-kingdom  of  Radiates  was 
represented  by  Corals  and  Crinoids;  that  of  Mollusks,  by 
species  of  all  the  grand  division  s,  among  which  the  Brachio- 


UPPER   SILURIAN. 


97 


pod  and  Orthoceras  tribes  were  the  most  prominent,  and 
especially  the  Brachiopod,  whose  shells  far  outnumber  those 


RADIATES  :  Fig.  154,  Zaphrontis  bilateral!*,  Clinton  group ;  155,  Favosites  Niagarensis,  Nia- 
gara group;  156,  Ilal.vsitcs  catcnulatus,  id.;  157,  Caryocrinus  ornatus,  id. — MOI.I.USKS: 
Fig.  158,  Pentamerus  oblongus,  Clinton  gr.;  159,  Orthis  biloba  (X  2),  Niagara  gr.  and  Dud- 
ley limestone;  160,  Leptama  transversalis,  id.;  161,  Strophomena,  id.;  162,  Uhyuclumella 
cuneata,  U.  S.  and  Great  Britain ;  lC3,Avicula  emacerabi,  Niag.  gr. ;  164,  Cyclonema  caiicellata, 
Clinton  gr.;  165.,  Platyceras  angulatum,  Niag.  gr.— ARTICULATES  :  Fig.  166,  Hoiualouotus 
delphinocephalus. 

of  all  other  Mollusks ;  that  of  Articulates,  by  Worms,  Ostra- 
coids,  and  Trilobites ;  and  before  the  close  of  the  era,  by  the 
new  form  of  Crustaceans  represented  in  fig.  174. 


»0  PALEOZOIC   TIME. 

1.  Radiates. — Fig.  154  is  a  polyp-coral  of  the  Cyathophyl- 
loid  tribe,  showing  the  radiating  plates  of  the  interior;  fig. 
155,  a  species  of  Favosites,  a  genus  in  which  the  corals  have 
a  columnar  structure,  and  horizontal  partitions  subdivide 

Figs.  167-175. 


MOLLUSKS:  Figs.  167,  168,  Pentamerns  galeatns;  169,  170,  Rhynchonella  ventricosa;  171, 
Spirifer  macropleurus ;  172,  Tentaculites  ornatus;  173,  id.  enlarged. — ARTICULATES;  Fig. 
174,  Eurypterus  remipes,  a  small  specimen;  175,  Leperditia  alta.  Species  all  from  the 
Lower  Ilelderberg  group. 

the  cells  within;  fig.  156,  Halysites  catenulatus,  called  chain- 
coral;  fig.  157,  a  Crinoid,  Caryocrinus  ornatus,  the  arms  at 
the  summit  broken  off;  fig.  89,  p.  57,  another  Crinoid  of  the 
family  of  Cystideans,  from  the  Niagara  group ;  fig.  87,  p.  57, 
a  star-fish,  also  from  the  Niagara  group. 

2.  Mottusks.— Figs.  158  to  162,  different  Brachiopods  of 
the  Niagara  period ;  figs.  167  to  171,  other  species  charac- 
teristic of  the  Lower  Helderberg  period;  figs.  164,  165, 
Gasteropods  of  the  Niagara  period ;  fig.  172,  small  slender 
tubular  cones,  called  Tentaculites,  almost  making  up  tho 


UPPER   SILURIAN.  99 

mass  of  some  layers  in  the  Lower  Helderberg ;  the  form  of 
one  of  them,  enlarged,  is  shown  in  fig.  173. 

3.  Articulates. — Fig.  166,  a  reduced  figure  of  a  common  Tri- 
lobite  of  the  Niagara  group,  a  species  of  Homalonotus,  often 
having  a  length  of  8  or  10  inches;  fig.  174,  Eurypterus 
remipes,  of  a  new  family  of  Crustaceans,  commencing  in  the 
Lower  Helderberg;  it  is  sometimes  nearly  a  foot  long; 
species  of  the  same  family  occur  in  Great  Britain  in  the 
Ludlow  beds,  and  one  of  them  is  supposed,  from  the  frag- 
ments found,  to  have  been  6  or  8  feet  long,  far  surpassing 
any  Crustacean  now  living;  fig.  175,  an  Ostracoid  Crusta- 
cean, the  Leperditia  alia,  of  unusually  large  size  for  the 
family,  modern  Ostracoids  seldom  exceeding  a  twelfth  of 
an  inch  in  length. 

In  the  Upper  Ludlow  beds  of  Great  Britain  a  few  remains 
of  land-plants  and  of  fishes  have  been  found.  But,  from  the 
similarity  of  many  fossils  of  the  upper  part  of  the  Ludlow 
beds  to  those  of  the  Upper  Helderberg,  it  is  probable  that 
these  Upper  Ludlow  beds,  if  referred  to  the  American  sys- 
tem of  subdivisions,  would  rank  as  Devonian. 

4.  General  Observations. 

1.  Geography. — On  the  map,  p.  69,  the  areas  over  which 
the  Silurian  formations  are  surface-rocks  are  distinguished 
by  being  horizontally  lined.  It  is  observed  that  they  spread 
southward  from  the  northern  Azoic. 

South  of  the  Silurian  area  commences  the  Devonian, 
which  is  vertically  lined ;  and  the  limit  between  them  shows 
approximately  the  course  of  the  sea-shore  at  the  close  of  the 
Silurian  age.  It  is  seen  that  more  than  half  of  New  York, 
and  nearly  all  of  Canada  and  "Wisconsin,  had  by  that  time 
become  part  of  the  dry  land ;  but  a  broad  bay  covered  the 
Michigan  region  to  the  northern  point  of  Lake  Michigan, 
for  here  Devonian  rocks,  and  to  some  extent  Carboniferous, 
were  afterwards  formed.  The  Azoic  dry  land,  the  back- 


100  PALEOZOIC   TIME. 

bone  of  the  continent,  had  also  received  additions  in  ,a  simi- 
lar manner  on  its  eastern  and  western  sides,  through  British 
America.* 

-But,  with  all  the  increase,  the  amount  of  dry  land  in  North 
America  was  still  small.  Europe  is  proved  by  similar  evi- 
dence to  have  had  much  undry  land.  The  surface  of  the 
earth  was  a  surface  of  great  waters,  with  the  continents 
only  in  embryo, — one  large  area  and  some  islands  represent- 
ing that  of  North  America,  and  an  archipelago  that  of 
Europe.  The  emerged  land,  moreover,  was  most  extensive 
in  the  higher  latitudes.  The  rivers  of  a  world  so  small  in 
its  lands  must  also  have  been  small.  The  lands,  too,  accord- 
ing to  present  evidence,  were  barren,  except  perhaps  during 
the  closing  part  of  the  age. 

The  succession  of  Upper  Silurian  formations  is  as  fol- 
lows:— (1)  The  coarse  grit  called  Oneida  conglomerate, 
occurring  of  great  thickness  along  the  Appalachian  region, 
and  reaching  north  to  central  New  York;  (2)  the  Medina 
sandstone,  also  very  thick  along  the  Appalachian  region, 
and  extending  northward  to  central  New  York,  and,  besides, 
spreading  westward  beyond  the  limits  of  that  State;  (3)  the 
Clinton  group  of  flags  and  shales,  having  the  same  Appala- 
chian extension  and  great  thickness,  but  spreading  on  the 
north  much  farther  westward,  even  to  the  Mississippi ; 

(4)  the  Niagara  group,  covering   the  Appalachian  region 
deeply  with  sandstone  and  shales,  and  New  York  with  shales 
and  limestones,  and  spreading  as  a  great  limestone  forma- 
tion through  the  larger  part  of  the  Interior  region ;  then 

(5)  the  limited  Salina  salt-bearing  marlites  of  New  York, 

*  On  the  map  referred  to,  page  69,  lines  of  the  Silurian  and  Devonian  are 
seen  to  extend  from  the  Hudson  River  southwestward  along  the  Appalachian 
region.  But  the  outcrop  of  the  Silurian,  here  represented,  is  not  evidence  that 
there  was  a  strip  of  dry  land  along  this  region  from  the  close  of  the  Silurian 
era,  because  there  is  proof  that  these  Appalachian  outcrops  are  a  consequence  of 
the  uplift  of  the  Appalachian  Mountains,  an  event  of  much  later  date.  (p.  155,) 


UPPER   SILURIAN.  101 

and  the  Appalachian  region  southwest,  with  some  cotempo- 
raneous  limestones  in  Canada;  then  (6)  another  limestone, 
but  impure  and  mostly  confined  to  New  York  State  and  the 
Appalachian  region.  These  facts  teach  that  geographical 
changes  took  place  from  time  to  time,  in  the  course  of  the 
era,  corresponding  to  these  several  changes  in  the  forma- 
tions. The  clear  continental  seas  of  the  Trenton  period 
were  succeeded  by  conditions  fitted  to  produce  the  several 
arenaceous  and  argillaceous  formations,  of  varying  limits, 
which  followed;  and  then  they  were  again  in  existence  at 
the  epoch  of  the  Niagara  group,  when  corals,  crinoids,  and 
shells  covered  the  bottom  of  the  continental  sea  and  made 
the  Niagara  limestone  formations.  But  the  pure  continental 
seas  in  the  Niagara  epoch  were  less  extended  than  those  of 
the  Trenton;  for  the  Appalachian  region,  instead  of  being 
part  of  the  pure  sea  and  making  limestones,  was  receiving 
great  depositions  of  sand  and  clay,  as  if  it  were  at  the  time 
a  broad  reef,  or  bank,  bordering  the  Atlantic  Ocean. 

The  Niagara  epoch  of  limestone-making  was  followed  by 
the  Salina  or  Saliferous  period.  As  the  beds  are  (1)  clays 
and  clayey  sands,  (2)  are  almost  wholly  without  fossils, 
and  (3)  afford  salt,  it  may  be  inferred  that  central  New 
York  was  at  the  time  a  great  salt  marsh,  mostly  shut  off 
from  the  sea.  Over  such  an  area  the  waters  would  at  times 
have  become  too  salt  to  support  life,  owing  to  partial  evapor- 
ation under  the  hot  sun,  and  too  fresh  at  other  times,  from 
the  rains.  Moreover,  muddy  deposits  would  have  been 
formed;  for  they  are  now  common  in  salt  marshes  wherever 
there  is,  as  there  was  then,  no  covering  of  yegetation,  and 
the  salt  waters  would  naturally  have  yielded  salt  on  evapor- 
ation in  the  drier  seasons.  Through  an  occasional  ingress 
of  the  sea,  the  salt  waters  might  have  been  re-supplied  for 
further  evaporation. 

There  is  direct  testimony  as  to  the  condition  of  the  land 
and  shallowness  of  the  waters  in  the  regions  where  many 


102  PALEOZOIC    TIME. 

of  the  rocks  were  in  progress;  for  ripple-marks  and  mud' 
cracks  are  common  in  some  layers,  and  are  positive  evidence 
that  the  sands  and  earth  that  are  now  the  solid  rock  were 
then  the  loose  sands  of  beaches,  sand-flats,  or  sea-bottoms,  or 
the  mud  of  a  salt  marsh.  Such  little  markings,  therefore, 
remove  all  doubt  as  to  the  condition  of  central  New  York 
in  the  Salina  period. 

Similar  markings  indicate,  also,  the  precise  condition  of 
the  region  of  the  Medina  sandstone,  showing  that  there  were 
sand-flats,  sea-beaches,  and  muddy  bottoms  open  to  the 
inflowing  sea.  Where  the  rill-marks  were  made  (fig.  19,  p. 
32)  the  sands  of  the  spot  were  those  of  a  gently  sloping  flat 
or  beach ;  the  waters  swept  lightly  over  the  sands,  dropping 
here  and  there  a  stray  shell  (as  the  Lingula  cuneatd)  or  a 
pebble,  which  became  partly  buried;  and  then,  as  they 
retreated,  they  made  a  tiny  plunge  over  the  little  obstacle 
and  furrowed  out  the  loose  sand  below  it.  The  firmness  of 
the  sand,  lightness  of  the  shells,  and  smallness  of  the  fur- 
rows are  proof  that  the  movements  were  light. 

The  great  thickness  of  the  several  formations  of  the  Upper 
Silurian  along  the  Appalachian  region  leads  to  many  inte- 
resting conclusions.  It  has  been  stated  (p.  92)  that  the 
Appalachian  formations  of  the  earlier  Silurian  were  equally 
remarkable  for  their  great  thickness.  The  Appalachian 
region, from  the  Primordial  era  onward,  was,  hence,  in  strong 
contrast  with  the  Interior  Continental  region,  where  the 
series  of  cotemporaneous  beds  are  hardly  one-tenth  as  thick. 
Taking  this  into  connection  with  another  fact,  that  very 
many  of  the  strata  among  the  thousands  of  feet  of  Silurian 
formations  in  the  Appalachian  region  contain  those  evidences 
of  shallow  water  and  mud-flat  or  sand-flat  origin  above  ex- 
plained, there  is  full  proof  that  in  the  Silurian  era  the  region 
was  for  the  most  part,  as  already  suggested,  a  vast  sand- 
reef,  ever  increasing  by  new  accumulations  under  the  action 
of  the  waves  and  currents  of  the  ocean  It  was  much  of 


UPPER    SILURIAN.  103 

the  time  a  great  barrier-reef  lying  between  the  open  ocean 
and  the  Interior  Continental  sea;  and  under  its  lee,  this 
inner  sea,  opening  southward  through  the  area  of  the  Mexi- 
can Gulf,  was  often  in  the  best  condition  for  the  growth  of 
the  shells,  corals,  and  crinoids  of  which  the  great  limestones 
were  made. 

While  the  Appalachian  region  was  alike  in  its  general 
condition  through  the  earlier  and  later  Silurian,  the  limits 
of  the  formations  in  progress  during  these  two  eras  were 
somewhat  different.  The  Green  Mountain  portions  of  the 
region  took  no  part  in  the  new  depositions  during  the  Upper 
Silurian  era.  The  fact  stated  on  page  91,  that  it  had  become 
part  of  the  comparatively  stable  and  emerged  portion  of  the 
continent,  is  thus  proved;  for  if  it  had  been  under  water, 
some  Upper  Silurian  beds  would  have  been  formed  about  its 
western  or  central  portions.  The  part  of  the  Appalachian 
region  which  participated,  during  the  Upper  Silurian  era,  in 
the  great  changes  connected  with  the  formation  of  rocks, 
extended  northward  from  Pennsylvania  into  New  York,  and 
not  along  the  Green  Mountains;  the  rocks  in  the  State  of 
New  York  have  great  thickness  for  some  distance  beyond 
the  Pennsylvania  border,  but  thin  out  about  the  centre. 

2.  Life. — In  the  Upper  Silurian  the  highest  species  of  the 
seas  and  of  the  world  continued  to  be  Mollusks,  of  the  order 
of  Cephalopods.  At  the  same  time,  Trilobites  were  the  first 
of  Articulates,  and  sea-weeds  the  highest  of  plants.*  Corals 
and  Crinoids  were  the  only  species  of  life  that  had  the  sem- 
blance of  flowers.  These  flower-animals  foreshadowed  the 
flowers  of  the  vegetable  kingdom  for  ages  before  any  of  the 
latter  existed. 

There  had  been,  however,  considerable  progress  in  the 
unfolding  of  the  system  of  life,  through  the  creation  of  new 
species  and  the  introduction  of  new  genera  and  families, 


Tho  only  exceptions  to  this  remark  yet  known  are  alluded  to  on  page  99. 
10 


104  PALEOZOIC   TIME. 

cotemporaneously  with  the  extinction  of  the  older  forms. 
In  the  Lower  Silurian  era  at  least  1000  species  of  animals 
became  extinct  in  America,  and  600  in  Great  Britain ;  and 
in  the  Upper  Silurian  800,  or  more,  in  America.  The  kind 
of  progress  which  was  exhibited  is  explained  on  a  future 
page. 


n.  AGE  OF  FISHES,  OR  DEVONIAN  AGE. 

1.  Subdivision. 

The  Devonian  Age  may  be  divided  into  two  eras, — an 
earlier  and  a  later, — or  that  of  the  lower  and  that  of  the  upper 
formations.  The  earlier  includes  the  periods  ORISKANY  and 
CORNIFEROUS  ;  the  later,  the  HAMILTON,  CHEMUNG,  and  CATS- 
KILL.  The  Oriskany  period  might  with  almost  equal  pro- 
priety be  annexed  to  the  Upper  Silurian.  The  distinction 
of  the  Catskill  from  the  Chemung  is  questioned. 

2.  Rocks:  kinds  and  distribution. 

1.  Earlier  and  Later  eras. — The  earlier  Devonian  is  remark- 
able for  a  great  limestone  formation,  which  spread  from 
New  York  over  a  large  part  of  the  Interior  region,  and 
nearly  equalled  the  Trenton  in  extent ;  while  the  later  has 
almost  no  limestones,  the  rocks  being  sandstones  and  shales 
with  some  conglomerates. 

2.  Oriskany  Period. — The  first  of  the  formations,  the  Oris- 
kany sandstone,  is  a  rough-looking,  earthy  rock.    It  extends 
along  the  Appalachian  region,  and  northward  in  New  York 
to  the  vicinity  of  Oriskany.     A  rock  of  the  same  age  occurs 
also  in  the  Eastern  border  region  in  Maine  and  Nova  Scotia. 
To  this  succeeds  the — 

8.  Corniferous  Period. — Its  lowest  rocks  are  fragmental 
beds,  called  the  Cauda-Galli  grit  and  the  Schoharie  grit, 
having  their  distribution  along  the  Appalachian  region, 


DEVONIAN    AGE.  105 

commencing  in  central  and  eastern  New  York  and  extend- 
ing south  westward. 

Next  follows  the  great  Corniferous  limestone,  the  lower 
part  of  which  is  sometimes  called  the  Onondaga  limestone, 
and  the  whole  often  the  Upper  Helderberg  group.  It  stretches 
from  eastern  New  York  westward  to  the  States  beyond  the 
Mississippi. 

The  name  Corniferous  (derived  from  the  Latin  cornu,  horn) 
was  given  it  by  Eaton,  from  its  frequently  containing  a  kind 
of  flint  called  hornstone. 

This  hornstone  differs  from  true  flint  in  being  less  tough, 
or  more  splintery  in  fracture,  though  it  is  like  it  in  hardness 
and  in  consisting  wholly  of  silica. 

The  limestone  is  literally  an  ancient  coral  reef.  It  con- 
tains corals  in  vast  numbers  and  of  great  variety;  and  in 
some  places,  as  near  Louisville,  Kentucky,  at  the  Falls  on 
the  Ohio,  the  resemblance  to  a  modern  reef  is  perfect.  Some 
of  the  coral  masses  at  that  place  are  6  or  8  feet  in  diameter; 
and  single  polyps  of  the  Cyathophylloid  corals  had  in  some 
species  a  diameter  of  2  and  3  inches,  and  in  one,  of  6  or  7 
inches. 

The  same  reef-rock  occurs  near  Lake  Memphremagog  on 
the  borders  of  Vermont  and  Canada;  but  the  corals  have 
there  been  partly  obliterated  by  metamorphism.  The  lime- 
stone occurs  among  mctamorphic  schists,  a  talcose  schist 
overlying  it,  according  to  Hitchcock.  The  crystalline  rocks 
extending  south  through  Vermont  into  Massachusetts,  and 
the  granites  and  gneiss  of  the  White  Mountains,  are  supposed 
to  be  altered  Devonian  sandstones  and  shales. 

4.  Hamilton  Period. — The  Hamilton  formation  consists  of 
sandstones  and  shales,  with  a  few  thin  layers  of  limestone. 
It  consists  of  three  parts,  corresponding  to  three  epochs : 
the  lower  part  is  called  the  Marcellus  shale;  the  middle,  the 
Hamilton  beds ;  and  the  upper,  the  Genesee  shale.  It  has 
its  greatest  thickness  along  the  Appalachians.  From  New 


106  PALEOZOIC   TIME. 

York  it  spreads  westward,  and,  in  the  form  of  what  is 
called  black  slate,  more  properly  a  black  shale  (supposed  to 
'be  of  the  epoch  of  the  Genesee  shale),  it  is  widely  knows 
through  the  Interior  Continental  region. 

The  Hamilton  beds  afford  an  excellent  flagging-stone  in 
central  New  York  and  on  the  Hudson  Eiver,  which  is  ex- 
tensively quarried  and  exported  to  other  States. 

5.  Chemung  Period. — The  Chemung  beds  are  mainly  sand- 
stones, or  shaly  sandstones,  with  some  conglomerate.  They 
spread  over  a  large  part  of  southern  New  York,  having 
great  thickness  in  the  Catskill  Mountains. 

The  formation  along  the  Appalachians  is  5000  feet  thick. 
It  thins  out  to  the  west  of  New  York,  in  Ohio,  and  Michigan. 

In  the  following  section,  taken  on  a  north-and-south  line 
south  of  Lake  Ontario,  No.  6  represents  the  beds  of  the 

Fig.  176. 


6  7  9  10  a 

Section  of  Devonian  formations  south  of  Lake  Ontario. 

Salina  period ;  overlaid  by  7,  the  Lower  Helderberg  lime- 
stone ;  9,  the  Corniferous,  or  Upper  Helderberg  limestone ; 
10,  a,  b,  c,  the  Hamilton  beds ;  and  11,  the  Chemung  group. 

6.  Catskill  Period.— The  Catskill  rocks  of  New  York  have 
been  considered  as  pertaining  to  a  Catskill  period ;  but  recent 
observations  have  shown  that  they  are  part  of  the  Chemung 
formation.  It  is  not  yet  known  that  the  same  is  true  of  the 
sandstones  and  shales  of  Pennsylvania,  referred  to  the  Cats- 
kill  period,  which  are  stated  to  have  a  thickness  of  6000  feet. 

In  Great  Britain,  the  Devonian  rocks  have  been  called 
the  Old  Red  Sandstone,  the  prevailing  rock  in  Wales  and 
Scotland  being  a  red  sandstone.  This  sandstone  formation, 
however,  includes  mai'ls  of  red  and  other  colors,  and  some 


DEVONIAN    AGE. 


107 


limestone.  The  distribution  in  Great  Britain  is  shown  on 
the  map,  p.  120.  In  Germany,  in  the  Rhenish  provinces,  there 
is  a  coral  limestone  very  similar  to  that  of  North  America. 

3.  Life. 

1.  General  characteristics. 

The  Devonian  of  North  America,  as  far  as  now  known,  is 
the  era  of  the  first  of  terrestrial  plants,  the  first  of  Insects  or 
terrestrial  Articulates,  and  the  first,  also,  of  Vertebrates.  These 
early  Vertebrates  were  Fishes, — the  species  that  belong  to  the 
water. 

2.  Plants. 

Figs.  177-179  represent  portions  of  some  of  the  plants. 
Fig.  179  is  a  fragment  of  afern,  and  figs.  177,  178,  portions 

Figs,  m-179-.      ,    . .  179 


PLANTS. — Fig.  177,  Lepidodendron  primppvnm,  from  the  Hamilton  group;  178,  Sigillaria, 
ibid.;  179,  Noeggerathia  Halliana,  from  the  Chemung  group. 

of  the  trees,  of  the  age.  The  scars  or  prominences  over  the 
surface  are  the  bases  of  the  fallen  leaves :  a  dried  branch  of 
a  Norway  spruce,  stripped  of  its  leaves,  looks  closely  like 
fig.  178.  By  referring  to  page  60,  it  will  there  be  seen  that 
among  the  Cryptogams  there  is  one  order,  the  highest,  or 
10* 


108  PALEOZOIC   TIME. 

that  of  AcrogenSj  in  which  the  plants  have  upward  growth 
like  ordinary  trees,  and  the  tissues  are  partly  vascular :  it  is 
the  one  containing  the  Ferns,  Lycopodia,  and  Equiseta.  The 
most  ancient  of  land  plants  belong,  to  a  great  extent,  to 
this  order, — the  highest  of  Cryptogams.  Another  portion  are 
related  to  the  lowest  order  of  flower-bearing  plants,  or  Pheno- 
gams,  called  Gymnosperms  (see  p.  61). 

The  groups  represented  under  these  divisions  are  the 
following  : — 

I.  FLOWERLESS  PLANTS,  or  CRYPTOGAMS,  Order  of  AGRO- 
GENS. 

1.  Fern  tribe. — The  species  have  a  general  resemblance  to 
the  ferns  or  brakes  of  the  present  time. 

2.  Lycopodium  tribe,  or  that  of  the  Ground-pine. — The  ex- 
isting plants  of  this  tribe  are  slender  species,  seldom  over  4 
or  5  feet  high :  some  of  the  ancient  were  of  the  size  of  forest- 
trees.     These  ancient  species  belong  mostly  to  the  Lepido- 
dendron  family,  in  which  the  scars  are  contiguous  and  are 
arranged  in  quincunx  order, — that  is,  alternate  in  adjoining 
rows, — as  shown  in  fig.  177.    The  Ground-pine  of  our  woods, 
although  flowerless  like  the  fern,  has  leaves  very  similar  to 
those  of  the  spruce  or  cedar  (Conifers) ;  and  this  type  of 
plants  is  intermediate  in  some  respects  between  the  Aero- 
gens  and  Gymnosperms  (Conifers). 

3.  Equisetum  tribe. — The  Equiseta  of  modern  wet  woods 
are  slender,  hollow,  jointed  rushes,  called  sometimes  scouring- 
rushes.   They  often  have  a  circle  of  slender  leaf-like  append- 
ages at  each  joint. 

The  Catamites,  or  tree-rushes,  are  peculiar  to  the  ancient 
world,  none  having  existed  since  the  Mesozoic.  They  had 
jointed  striated  stems  like  the  Equiseta,  and  otherwise 
resembled  them.  But  they  were  often  a  score  of  feet  or 
more  in  height,  and  sometimes  6  inches  in  diameter.  Some 
of  them  had  hollow  stems  like  the  Equiseta;  others  had  the 
interior  of  the  stems  woody,  and  these  were  intermediate  in 


DEVONIAN    AGE.  109 

some  respects  between  the  Equiseta  and  the  Gymnosperms. 
Fig.  225,  under  the  Carboniferous  age,  represents  a  portion 
of  one  of  these  plants 

II.  FLOWERING  PLANTS,  or  PHENOGAMS,  of  the  Order  of 
GYMXOSPERMS 

1.  Conifers. — The  species  are  related  to  the  common  pines 
and  spruces,  or  more  nearly  to  the  Araucarian  pines  of 
Australia  and  South  America.     The  fossils  are  merely  por- 
tions of  the  trunk  or  branches.     It  has  been  suggested  by 
Mr.  Lesquereux  that  all  the  specimens  belong  to  the  follow- 
ing tribe  : — 

2.  SigiUarids. — The    Siyillarice  were    treos   of    moderate 
height,  with  stout,  sparingly-branched  trunks,  bearing  long 
linear  leaves  much  like  those  of  the  Lepidodendra.     The 
scars  on  the  exterior  are  mostly  in  parallel  vertical  lines,  as 
in  fig.  178  and  fig.  222.  p.  127,  and  not  in  quincunx  order, 
like  those  of  the  Lepidodendra. 

The  earliest  fossil  land-plants  thus  far  found  in  the  United 
States  occur  in  the  Hamilton  formation.  Whether  they 
occur  lower  than  this,  or  in  earlier  Devonian,  in  Canada 
and  New  Brunswick,  is  not  certain. 

Conifers,  Ferns,  and  Lepidodendra  have  also  been  reported 
from  some  of  the  Devonian  beds  of  Britain  and  Europe.  The 
earliest  remains  found  in  Great  Britain  occur  in  the  lowest 
Devonian,  and  also  in  the  Upper  Ludlow  beds  (p.  99). 

The  hornstone  develops,  under  the  microscope,  the  fact 
that  it  was  probably  made  from  the  siliceous  remains  of 
plants  and  animals.  Figs.  180  to  194  represent  some  of  the 
species  which  have  been  detected  by  Dr.  M.  C.  White  in 
specimens  from  New  York  and  elsewhere.  Figs.  180  to  186 
are  microscopic  plants,  related  to  the  Desmids;  fig.  187  is 
another  kind,  called  a  Diato?n,  a  kind  which  forms  siliceous 
shells,  and  which  is  probably  one  of  the  sources  of  the 
silica  of  which  the  hornstone  was  made  (See,  on  Diatoms 
and  Desmids,  p.  61.)  Figs.  188, 189  are  spicules  of  Spongee, 


110  PALEOZOIC   TIME. 

also  siliceous,  and  another  of  the  sources  of  the  silica.  Figs. 
190-192  are  probably  also  sponge-spicules.  Figs.  193, 194  are 
fragments  of  the  teeth  of  some  Gasteropod  Mollusk.  The 
last  is  from  a  hornstone  of  the  Trenton  period  (Silurian) 
which  was  found  to  afford  the  same  evidences  of  organic 
origin. 

3.  Animals. 

The  early  Devonian  was  the  coral  period  of  the  ancient 
world.  In  no  age  before  or  since,  not  even  the  present,  have 
coral  reefs  of  greater  extent  been  formed. 

Among  Mollusks,  Brachiopods  were  still  the  prevailing 
kinds,  though  ordinary  Bivalves  or  Conchifers,  and  Uni- 


Microscopic  Organisms  from  the  Hornstono. 

valves  or  Gasteropods,  were  more  abundant  than  in  the 
Silurian.  A  new  type  of  Cephalopods  commenced  in  tho 
Middle  Devonian.  Hitherto,  the  partitions  or  septa  in  tho 
shells,  straight  or  coiled,  were  flat  or  simply  concave;  but 
in  the  new  genus  Goniatites,  the  margin  of  the  plate  has  one 
or  more  deep  angles,  one  of  the  angles  being  at  the  middle 
of  the  back  of  the  shell.  The  name  is  from  the  Greek  gonu, 
knee  or  angle. 

Among  Articulates,  there  were  "Worms  and  Crustaceans 
as  in  earlier  time,  and  the  most  common  Crustaceans  were 
Trilobites.  Besides  these  there  were  the  first  of  Insects,  the 
wings  of  some  species  having  been  reported  from  the  Devo- 
nian of  New  Brunswick. 


DEVONIAN   AGE. 

Figs.  195-200. 


Ill 


RADIATES.— Fig.  195,  Zaphrentis  Rafinesqnii;  196,  197,  Cyathophyllum  rngosnm;  198, 
Syringopora  Maclurii;  199,  Aulopora  cornuta;  200,  Fayosites  Goldfussi:  all  of  the  Cornif- 
erous  period. 

1.  Radiates. — Fig.  195,  one  of  the  Cyathophylloid  corals, 
Zaphrentis  Rafinesquii;  fig.  196,  another,  Cyathophyllum  rugo- 
sum,  both  from  the  Falls  of  the  Ohio,  and  the  latter  forming 
very  large  masses.      Fig.  197  is  a  top  view  of  the  cells  in 
fig.  196.   Fig.  200,  a  Favosites  from  the  same  locality,  showing 
well  the  columnar  structure  characterizing  the  genus:  the 
species  F.  Goldfussi  occurs  both   in  America  and  Europe. 
Figs.  198  and  199  are  small  corals  from  Canada  West. 

2.  Mollusks.— Figs.  201    to    203,    Brachiopods    from   the 
Hamilton  beds;  figs.  204,  205,  Conchifers,  from  the  same; 
fig.  206,  Goniatites  Marcellensis,  ib. ;  fig.  207,  a  view  of  the 
back,  showing  the  angles  in  the  partitions,  this  species  hav- 
ing only  one  angle  or  re-entering  lobe. 

3.  Articulates. — Fig.  208,  the  Trilobite  Phacops  Bufo. 

4.  Vertebrates. — The  fishes  of  the  Devonian  belong  to  two 
orders :  the  Ganoid  and  the  Selachian  (see  p.  51).     Some  of 
the  Ganoids  are  represented  in  figs.  210  to  216.     The  fishes 
of  this  order  are  related  in  several  points  to  Eeptiles.    Unlike 
ordinary  fishes  (or  the  Teliosts) — (1)  they  have  the  power 
of  moving  the  head  up  and  down  at  the  articulation  between 


PALEOZOIC    TIME. 


the  head  and  the  body,  the  articulation  being  made  by  means 
of  a  convex  and  concave  surface ;  (2)  the  air-bladder,  which 


Figs.  201-208. 


MOLLCSKS. — Fig.  201,  Atrypa  aspera;  202,  Spirifer  mncronatns ;  203,  Chonetes  setigera;  204. 
Grammysia  Hamiltonensis;  205,  Microdon  bellistriatus ;  206,  207,  Goniatites  Marcellensis. 
all  from  the  Hamilton  group.  ARTICULATES  :  Fig.  20S,  PLacops  Bufo,  from  the  Hamilton 
group. 

answers  to  the  lung  of  higher  animals,  has  a  cellular  or 
lung-like  structure,  thus  approximating  to  air-breathing 
species ;  (3)  the  teeth  have  in  general  a  structure  like  that 
of  some  early  Keptiles.  Fig.  210  is  a  reduced  view  of  a  Ganoid 
with  large  plates  over  the  body,  like  a  Turtle :  moreover,  it 
moved  by  means  of  paddles  instead  of  its  tail,  the  principal 
organ  of  motion  in  most  Fishes,  and  in  this,  also,  it  resembles 


DEVONIAN    AGE. 


113 


Turtles.    It  is  the  Pterichthys  of  Agassiz,  a  name  signifying 
winged  fish.    There  is  another  plate-covered  kind,  one  genus 

Figs.  209,  210. 


VEBTEBBATES.— Fig.  209,  Fin-spine  of  a  Shark  (X  %);  210,  Pterichthys  Milleri  (X%). 

of  which  is  named  Coccosteus,  which  wants  the  paddles,  and 
sculled  itself  along  with  the  tail,  like  most  Fishes.  Fig.  211 
represents  a  different  type  of  Ganoid,  the  Cephalaspis,  having 
a  flat  and  broad  plate-covered  head,  with  rhombic  scales 
over  the  body :  figs.  212  show  the  forms  of  some  of  the 
scales.  Fig.  215  is  another,  a  species  of  Dipterus,  covered 
with  rhombic  scales,  put  on,  as  in  the  preceding,  much  as 
tiles  are  arranged  on  a  roof:  fig.  216  is  one  of  the  scales, 
natural  size.  Fig.  213  is  another  type  of  Ganoids,  having 
the  scales  rounded  and  set  on  more  like  shingles  ;  it  is  a  Holo- 
ptychius :  fig.214  represents  a  scale,  natural  size.  These  figures 
are  all  much  reduced.  Scales  of  a.  HoloptycJiius  have  been  found 
in  Chemung  beds  which  were  over  an  inch  and  a  half  broad, 
indicating  the  existence  of  fishes  of  great  size. 


114 


PALEOZOIC    TIME. 


The  Selachians,  or  species  of  the  shark  tribe,  belong  to  the 
family  of  Cestracionts  (p.  52),   or  that  in  which  the  mouth 


Figs.  211-216. 
11 


GANOIDS.—  Fig.  211,  Cephalaspis  Lyellii  (X%,);  212,  Scales;  213,  Holoptychius 
Scale  ;  215,  Dipterus  macrolepidotus  (X  14)  ;  216,  Scale. 


;  214, 


has  a  pavement  of  broad  bony  pieces  for  grinding.  The 
food  in  the  seas  for  these  carnivorous  Fishes  consisted  mainly 
of  shell-fish  and  mail-clad  Ganoids;  and  grinders  were,  there- 
fore, better  suited  for  the  times  than  cutting  teeth.  Many 
of  these  Cestraciont  sharks  were  of  very  large  size.  Fig. 
209  represents  a  fin-spine  of  one,  drawn  two-thirds  its  actual 
size,  found  in  the  Corniferous  beds  of  the  State  of  New  York. 


DEVONIAN    AGE.  115 

The  remains  of  Fishes  in  the  rocks  are  numerous  after  the 
first  appearance  of  them. 

4.  General  Observations. 

1.  Geography. — During  the  Silurian  there  had  been  a  gra- 
dual gain  of  dry  land  on  the  north,  extending  the  Azoic  con- 
tinent (p    73)  southward.    This  gain  continued  through  the 
Devonian,  so  that  the  beds  of  the  next  age,  the  Carbon- 
iferous, extend  only  a  short  distance  north  of  the  southern 
boundary  of  New  York.    The  sea-shore  was  thus  being  set 
farther  and  farther  southward  with  the  progressing  periods. 

The  formations  have  their  greatest  thickness  along  the 
Appalachian  region,  as  in  the  Silurian  Age.  And  both  this 
fact  and  their  successions  lead  to  similar  general  conclu- 
sions to  those  stated  on  page  102. 

2.  Life. — The  great  feature  of  the  Devonian   age   is  the 
introduction  of  the  first  of  terrestrial  plants,  the  first  of  ter- 
restrial animals  (Insects),  and  the  first  of  Vertebrates.     It 
is  possible  that  future  discovery  may  throw  farther  back  in 
time  the  commencement  of  these  types.    However  this  may 
be,  whenever  the  first  land-plant  appeared,  it  was  an  epoch 
of  great  progress  in  the  system  of  life  on  the  earth.    It  was 
a  change  from  the  leafless  Sea-weed  to  Ferns,  Lepidodendra, 
and  Pines, — from  a  bare  and  lifeless  world  above  tide-level 
to  one  of  forest-clad  hills. 

This  step  of  progress  from  Sea-weeds  to  Ferns,  Lycopo- 
dia,  and  Pines  was  not  made  by  a  gradual  working  upward 
through  Mosses  and  other  low  forms  of  Cryptogams.  On 
the  contrary,  no  Mosses,  although  many  are  true  marsh- 
species,  appear  to  have  been  in  existence  until  long  after  the 
close  of  the  Carboniferous  age.  It  was  a  sudden  advance 
from  the  lowest  to  the  highest  of  Cryptogams. 

In  the  same  manner,  with  regard  to  Fishes,  the  earliest 
species  belong  to  the  two  highest  groups  of  the  class, — the 
Sharks  and  Ganoids;  and  both  are  above  the  level  of  the 


116  PALEOZOIC   TIME. 

fish, — the  Ganoids  being  partly  Eeptilian.  There  is  not  the 
least  evidence  of  any  development  upward  from  the  Mollusk, 
Worm,  or  Trilobite  to  these  Fishes,  or  of  a  gradual  rise  in 
the  grade  of  Fishes  from  the  lower  to  the  highest.  The 
Devonian  Fishes  are  often  of  great  size  and  eminently  com- 
plete and  perfect  in  their  parts.  Their  introduction  into 
the  system  of  life  was  a  no  less  sudden  step  upward  than 
in  the  case  of  plants. 

There  are  here  no  facts  sustaining  the  theory  that  species 
were  made  from  species  by  a  natural  process  of  growth  or 
development.  Without  any  known  natural  method  of  crea- 
tion to  appeal  to,  Science  is  led  rightly  to  ascribe  the  exist- 
ence of  plants  and  animals,  each  in  its  time  and  place,  to 
Him  alone  who  created  "  in  the  beginning." 


HI.  CARBONIFEROUS  AGE,  OR  AGE  OF  COAL 
PLANTS. 


1.  General  Characteristics:  Subdivision, 

The  Carboniferous  age  was  remarkable,  in  general,  for  — 

(1.)  The  wide  limits  of  the  continents  above  the  sea-level. 

(2.)  The  extent  of  the  low  marshy  or  fresh-water  areas 
over  these  continents,  and  the  flat  or  gently  undulating 
surface  of  nearly  all  the  rest  of  the  emerged  land,  few  ele- 
vated ridges  existing  any  where. 

(3.)  The  luxuriant  vegetation,  clothing  the  land  with 
forests  and  jungles. 

(4.)  The  existence  of  Insect  life  over  the  land,  and  of 
Amphibians  and  other  Reptiles  in  the  marshes  and  seas. 

But,  while  having  these  as  its  main  characteristics,  it  was 
not  an  age  of  continued  verdure.  There  was,  first,  a  long 
period  —  the  Subcarboniferous  —  in  which  the  land  was  mostly 
beneath  the  sea;  for  limestone,  full  of  marine  fossils,  is  the 


CARBONIFEROUS   AGE  117 

prevailing  rock,  and  there  are  but  thin  coal  seams  in  some 
regions  of  sandstones  and  shales.  This  period  was  followed 
by  the  Carboniferous,  or  that  of  the  true  Coal  measures.  Yet 
even  in  this  middle  period  of  the  age  there  were  alterna- 
tions of  submerged  with  emerged  continents,  long  eras  of 
dry  and  marshy  lands  luxuriantly  overgrown  with  shrub- 
bery and  forest-trees  intervening  between  other  long  eras 
of  great  barren  continental  seas.  Then  there  was  a  closing 
period, — the  Permian, — in  which  the  ocean  prevailed  again, 
though  with  contracted  limits;  for  the  rocks  are  mainly  of 
marine  origin. 

The  Carboniferous  period  and  age  were  so  named  from  the 
fact  that  the  great  coal  beds  of  the  world  originated  mainly 
during  their  progress.  The  term  Permian  was  given  to  the 
rocks  of  the  third  period  by  Murchison,  de  Verneuil  and 
Keyserling,  from  a  region  of  Permian  rocks  in  Eussia,  the 
ancient  kingdom  of  Permia,  now  divided  into  the  govern- 
ments of  Perm,  Viatka,  Kasan,  Orenberg,  etc. 

2.  Distribution  of  Carboniferous  Rocks,  ^^^\ 
The  Carboniferous  areas  on  the  map  of  the  United  States, 
p.  69,  are  the  dark  areas ;  the  black  cross-lined  with  white 
being  the  Subcarboniferous;  the  pure  black,  the  Carbonife- 
rous; the  black  dotted  with  white,  the  Permian.  The  last 
occur  only  west  of  the  Mississippi. 

The  following  are  the  positions  of  the  several  great  areas 
in  North  America : — 

I.  EASTERN  BORDER  EEGION. — (1.)  The  Rhode  Island  area, 
extending  from  Newport  in  Ehode  Island  to  Worcester  in 
Massachusetts. 

(2.)  The  Nova  Scotia  and  New  Brunswick  area. 

II.  APPALACHIAN  and  INTERIOR  EEGIONS. — (1.)  The  great 
Appalachian  area,  extending  from  the  southern  borders  of 
New  York  and  Ohio  southwestward  to  Alabama,  covering 
the   larger  part   of  Pennsylvania,  half   of  Ohio,  part  of 


118 


PALEOZOIC    TIME. 


Kentucky  and  Tennessee,  and  a  little  of  Mississippi.  To 
the  northeast,  in  Pennsylvania,  this  coal  field  is  much 
broken  into  patches,  as  shown  in  the  accompanying  map  of 


a  part  of  the  State,  the  black  areas  being  those  of  the  coal 
district. 

(2.)  The  Michigan  area,  covering  the  cefntral  part  of  the 
State. 


CARBONIFEROUS   AGE.  119 

(3.)  The  Illinois  and  Missouri  area,  or  that  of  the  Missis- 
sippi basin,  covering  much  of  Illinois,  and  part  of  Indiana, 
Kentucky,  Iowa,  Minnesota,  Missouri,  Kansas,  and  Arkansas, 
and  stretching  southward  into  northern  Texas. 

(4.)  The  Rocky  Mountain  area,  situated  in  some  parts  of  the 
summits  of  the  Rocky  Mountains,  as  around  the  Great  Salt 
Lake  in  Utah. 

III.  ARCTIC  REGION. — The  Melville  Island,  and  those  of 
other  islands  between  Grinnell  Land  and  Banks  Land, 
mostly  north  of  latitude  70°. 

The  areas  of  workable  coal  measures  are  estimated  as 
follow  :— 

1.  Rhode  Island 1,000  square  miles. 

2.  Nova  Scotia  and  New  Brunswick  18,000       "  " 

3.  Appalachian 60,000       "  « 

4.  Michigan 5,000       "  " 

5.  Illinois  and  Missouri 60,000        "  " 

The  total  for  the  whole  United  States  is  about  130,000 

square  miles. 

Carboniferous  strata  occur  also  in  Great  Britain  and 
various  parts  of  Europe.  Those  of  England  are  distributed 
over  an  area  between  South  Wales  on  the  west  and  the 
Newcastle  basin  on  the  northeast  coast  (as  shown  by  the 
black  areas  on  the  following  map),  the  most  important  for 
coal  being  the  South  Wales  region ;  the  Lancashire  district, 
bordering  on  Manchester  and  Liverpool;  the  Yorkshire, 
about  Leeds  and  Sheffield ;  and  the  Newcastle. 

Scotland  has  some  small  areas  between  the  Grampian 
range  on  the  north  and  the  Lammermuirs  on  the  south ;  and 
Ireland,  several  coal  regions  of  large  extent,  as  at  Ulster, 
Connaught,  Leinster  (Kilkenny),  and  Munster. 

The  coal-fields  of  Europe  which  are  most  worked  are  tho 
Belgian,  bordering  on  and  passing  into  France.  Germany 
contains  only  small  c'oal-bearing  areas;  and  Russia  in  Europe 
11* 


120 


PALEOZOIC   TIME. 

Fig.  218. 


Fig.  218,  Geological  Map  of  England.  The  areas  lined  horizontally  and  numbered  1  are 
Silurian.  Those  lined  vertically  (2),  Devonian.  Those  cross-lined  (3),  Subcarboniferous. 
Carboniferous  (4),  black.  Permian  (5).  Those  lined  obliquely  from  right  to  left,  Triassie  (6), 
Lias  (7  a),  Oolite  (7  b),  Wealden  (8),  Cretaceous  (9).  Those  lined  obliquely  from  left  ta 
right  (10, 11),  Tertiary.  A  is  London,  B,  Liverpool,  C,  Manchester,  D,  Newcastle. 


CARBONIFEROUS   AGE.  121 

almost  none,  although  the  Subcarboniferous  and  Permian 
rocks  cover  large  portions  of  the  surface. 

The  following  are  the  areas  oi  some  of  the  foreign  coal 
districts : — 

Great  Britain  and  Ireland 12,000  square  miles. 

Spain 4,000        "         « 

France 2,000?      "         " 

Belgium 518         "         " 

or  less  than  20,000  square  miles,  against  148,000  in  North 
America. 

Valuable  coal  beds  are  not  found  in  any  rocks  older  than 
the  Carboniferous,  although  black  bituminous  slates  are  not 
uncommon  even  in  the  Lower  Silurian.  They  occur,  how- 
ever, in  different  Mesozoic  formations,  and  also  occasionally 
in  the  Cenozoic,  but  not  of  the  extent  which  they  have  in 
the  Carboniferous  formations. 

3.  Kinds  of  Rocks.  \^(j,  *•" 

1.  SUBCARBONIFEROUS    PERIOD.  —  The    Subcarboniferous 
strata  in  the  Interior  Continental  region  are  mainly  lime- 
stone ;  and,  as  the  limestone  abounds  in  many  places  in  Cri- 
noidal  remains,  the  rock  is  often  called  the  Crinoidal  limestone. 
In  the  Appalachian  region,  in  middle  and  southern  Virginia, 
the  rock  is  also  limestone,  and  has  great  thickness ;  but  in 
northern  Virginia  and  Pennsylvania  it  is  mostly  a  sandstone 
or  conglomerate  overlaid  by  a  shaly  or  clayey  sandstone  and 
marlite  of  reddish  and  other  colors, — the  whole  having  a 
maximum  thickness  of  5000  to  6000  feet.    In  the  Eastern 
border  region,  in  Nova  Scotia,  the  rocks  are  mostly  reddish 
sandstone  and  marlite,  with  some  limestone, — the  estimated 
thickness  6000  feet. 

The  prevailing  rock  in  Great  Britain  and  Europe  is  a 
limestone,  called  there  the  Mountain  limestone. 

2.  CARBONIFEROUS  PERIOD. — (1.)  Bocks  of  the  Coal  forma- 
tion.— The  rocks  of  the  Carboniferous  period — that  is,  those 


122  PALEOZOIC   TIME. 

of  the  Coal  measures — are  sandstones,  shales,  conglomerates, 
and  occasionally  limestones ;  and  they  are  so  similar  to  the 
rocks  of  the  Devonian  and  Silurian  ages  that  they  cannot 
be  distinguished  except  by  the  fossils.  They  occur  in  various 
alternations,  with  an  occasional  bed  of  coal  between  them. 
The  coal-beds,  taken  together,  make  up  not  more  than  one- 
fiftieth  of  the  whole  thickness ;  that  is,  there  are  50  feet  or 
more  of  barren  rock  in  the  coal  formation  to  1  foot  of  coal. 
An  example  of  the  alternations  is  given  in  the  following 
section : — 

1.  Sandstone  and  conglomerate  beds 120   feet. 

2.  COAL 6    " 

3.  Fine-grained  shaly  sandstone 50     " 

4.  Siliceous  iron-ore 1^  " 

5.  Argillaceous  sandstone 75     " 

6.  COAL,  upper  4  feet  shale,  with   fossil  plants,  and  below  a  thin 

clayey  layer 7  «• 

7.  Sandstone 80  " 

8.  Iron-Ore ]  • 

9.  Argillaceous  shale., 80  ' 

10.  LIMESTOM?  (oolitic),  containing  Product!,  Crinoids,  etc 1J  •• 

11.  Iron- Ore,  with  many  fossil  shells 3  •' 

12.  Coarse  sandstone,  containing  trunks  of  trees 25  " 

13.  COAL,  lying  on  1  foot  slaty  shale  with  fossil  plants 5  • 

14.  Coarse  sandstone 12  4< 

The  limestone  strata  are  more  numerous  and  extensive 
in  the  Interior  Continental  region  than  in  the  Appalachian, 
and  west  of  the  States  of  Missouri  and  Kansas  limestone  is 
the  prevailing  rock. 

Beds  of  argillaceous  iron-ore  are  very  common  in  coal 
districts,  so  that  the  same  region  affords  ore  and  the  coal 
for  smelting  it.  Some  of  the  largest  iron-works  in  the  world. 
on  both  sides  of  the  Atlantic,  occur  in  coal  districts. 

The  coal  beds  often  rest  on  a  bed  of  grayish  or  bluish  clay, 
called  the  under-day,  which  is  filled  with  the  roots  or  stems 
of  plants.  "When  this  under-clay  is  absent,  the  rock  is 
usually  a  sandstone  or  shale.  Above  the  coal,  the  rock  may 


CARBONIFEROUS    AGE.  123 

be  sandstone,  shale,  conglomerate,  or  even  limestone;  often 
the  layer  next  above,  especially  if  shaly,  is  filled  with  fossil 
leaves  and  stems.  In  some  cases,  trunks  of  old  trees  rise 
from  the  coal  and  extend  up  through  overlying  beds,  as  in 
the  annexed  figure,  by  Dawson,  from  the  Nova  Scotia  Coal 
measures.  Occasionally,  as  in  Ohio,  logs  50  to  60  feet  long 
lie  scattered  through  the  sandstone  beds,  looking  as  if  a 
forest  had  been  swept  off  from  the  land  into  the  sea. 

(2.)   Coal  beds. — The  coal  beds  vary  in  thickness  from  a 
fraction  of  an  inch  to  30  or  40  feet,  but  seldom  exceed  8  feet, 

Fig.  219. 


Section  of  a  portion  of  the  Coal  measures  at  the  Joggins,  Nova  Scotia,  having  erect  stumpfl, 
and  also  "  rootlets"  in  the  under-clays. 

and  are  generally  much  thinner :  8  feet  is  the  thickness  of 
the  principal  bed  at  Pittsburg,  Pa.;  29  J  feet,  that  of  ,be 
"  Mammoth  Vein"  at  Wilkesbarre,  Pa. ;  37*  feet,  that  of  one 
of  the  two  great  beds  at  Pictou  in  Nova  Scotia.  In  these 
thick  beds,  and  often  also  in  the  thin  ones,  there  are  some 
intervening  beds  of  shale,  or  of  very  impure  coal,  so  that 
the  whole  is  not  fit  for  burning. 

The  coal  varies  in  kind  according  to  the  proportion  of 
bituminous  substances  present, — that  containing  little  or 
none  being  called  Anthracite,  and  the  rest  Bituminous  coal 
(see  p.  18).  When  only  10  or  15  per  cent,  of  bituminous 
substances  are  present,  it  is  often  called  Semi-bituminous  coal. 
In  Pennsylvania  the  coal  of  the  Pottsville,  Lehigh,  and 
Wilkesbarre  regions  is  anthracite;  that  of  Pittsburg,  bitumi- 


124  PALEOZOIC   TIME. 

nous  coal;  and  that  of  part  of  the  intermediate  district, 
semi-bituminous,  as  so  designated  on  the  map,  page  118. 

The  coal  also  varies  as  to  the  impurities  present.  All  of 
it  contains  more  or  less  of  earthy  material,  as  clay  or  silica; 
and  this  earthy  material  constitutes  the  ashes  and  slag  of  a 
coal  fire.  Ordinary  good  anthracite  contains  7  to  12  pounds 
of  impurities  in  a  hundred  pounds  of  coal.  In  some  coal 
beds  there  is  considerable  pyrites  or  sulphuret  of  iron  (a 
compound  of  sulphur  and  iron),  and  the  coal  is  then  unfit 
for  use.  It  is  seldom  that  pyrites  is  altogether  absent.  The 
sulphur  gases  which  are  perceived  in  the  smoke  or  gas  from 
a  coal  fire  come  usually  from  the  decomposition  of  pyrites. 

Mineral  coal,  although  it  seldom  breaks  into  plates  unless 
quite  impure,  still  consists  of  thin  layers.  This  is  shown  in 
the  hardest  anthracite  by  a  delicate  banding  of  a  surface  of 
fracture,  as  may  be  readily  seen  when  it  is  held  up  to  the 
light.  This  structure  is  absent  in  the  variety  called  Cannel 
coal,  which  is  a  bituminous  coal,  very  compact  in  texture, 
feeble  in  lustre,  and  smooth  and  often  flint-like  in  fracture. 

(3.)  Mineral  Oil. — Besides  mineral  coal,  the  rocks  some- 
times afford  bituminous  liquids,  called  ordinarily  petroleum, 
or  mineral  oil,  or,  when  purified  for  burning,  kerosene,  and 
sometimes  mineral  naphtha.  Oil-wells  are  largely  worked  at 
Titusville  in  Pennsylvania,  and  at  Mecca  in  Trumbull  co., 
Ohio ;  and  it  is  probable  that  the  material  at  each  of  these 
places  proceeds  from  the  lower  Subcarboniferous  rocks, 
though  possibly  from  the  Devonian.  Petroleum  is  a  result 
of  the  decomposition  of  vegetable  substances.  It  proceeds 
from  rocks  of  various  ages, — from  those  of  the  Lower  Silu- 
rian to  the  Tertiary,  The  earliest  springs  affording  a  large 
supply  of  oil  come  from  the  Corniferous  beds  (Devonian), 
as  at  Enniskillen  in  Canada. 

(4.)  Salt  or  Salines. — The  Subcarboniferous  formation  in 
Michigan,  at  Grand  Eapids  and  the  adjoining  region,  affords 
extensive  salines,  and  there  are  many  wells  opened  by 


CARBONIFEROUS   AGE.  125 

boring.  The  beds  affording  the  saline  waters  consist  of 
clayey  beds  or  mu.lites,  shale,  and  magnesian  limestone,  and 
abound  also  in  gypsum,  thus  resembling  those  of  the  Salina 
period  in  New  York  (p.  95). 

3.  PERMIAN  PERIOD. — The  rocks  of  the  Permian  beds  are 
mostly  sandstones  and  marlites,  with  some  impure  or  mag- 
nesian limestones,  and  gypsum.  They  occur  in  North  Ame- 
rica west  of  the  Mississippi  in  Kansas,  and  about  some  parts 
of  the  eastern  slope  of  the  Eocky  Mountains,  where  they  lie 
conformably  over  the  Carboniferous.  Similar  rocks  occur  in 
Great  Britain  in  the  vicinity  of  several  of  the  coal  regions, 
and  also  in  Germany  and  Russia.  Thin  seams  of  coal  are 
occasionally  interstratified  with  the  sandstones,  but  none  of 
workable  extent  are  known. 

4.  Life. 
1.  Plants. 

The  plants  of  the  forests,  jungles,  and  floating  islands  of 
the  Carboniferous  Age,  thus  far  made  known,  number  about 
900  species.  Among  the  fossils  there  are  none  that  afford 
satisfactory  evidence  of  the  presence  of  either  Angiosperms 
or  Palms  (p.  62) ;  for  no  net-veined  leaves,  allied  in  charac- 
ter to  those  of  the  Oak,  Maple,  Willow,  Hose,  etc.,  have  been 
found  among  them ;  and  no  palm-leaves  or  palm-wood.  More- 
over, the  plains  were  without  grass,  and  the  swamps  and 
woods  without  moss.  At  the  present  day  Angiosperms 
along  with  Conifers,  or  the  Pine  family,  make  up  the  great 
bulk  of  our  shrubs  and  forest-vegetation;  Palms  abound 
in  all  tropical  countries;  grass  covers  all  exposed  slopes 
where  the  climate  is  not  too  arid ;  and  mosses  are  the  prin- 
cipal vegetation  of  most  open  marshes. 

The  view  in  fig.  220  gives  some  idea  of  the  Carbon- 
iferous vegetation  over  the  plains  and  m.arshes  of  the  era. 

The  Carboniferous  species,  like  their,  predecessors  in  the 
Devonian  age,  belonged  to  the  following  groups : — 


126 


PALEOZOIC   TIME. 


I.  CRYPTOGAMS,  or  Flowerless  Plants,  Order  of  ACROGENS 

(1.)  Fern  tribe. — Ferns  were  very  abundant,  a  large  part  of 

the  fossil  plants  of  a  coal  region  being  their  delicate  fronds 


Fig.  220. 


Carboniferous  Vegetation. 


(usually  called  leaves).  One  of  them  is  represented  in  fig. 
224.  Besides  small  species,  like  the  common  kinds  of  the 
present  day,  there  were  tree-ferns,  species  that  had  a  trunk, 
perhaps  15  or  20  feet  high,  and  which  bore  at  top  a  radiating 
tuft  of  the  very  large  leaf-like  fronds,  resembling  the 


CARBONIFEROUS    AGE. 


127 


modern  tree-fern  of  the  tropics.  One  of  the  tree-ferns  of  the 
Pacific  is  represented  in  fig.  220,  near  the  middle  of  the  view, 
and  smaller  ferns  in  front  of  it  below.  Tree-ferns,  however, 


Figs.  221-226. 


Fig.  221,  Lepidodendron  obovatum;  222,  Sigillaria  oculata;  223,  Stigmaria  ficoides;  224, 
Sphenopteris  Gravenborstii ;  225,  Calamites  cannseformis ;  226,  Trigonocarpum  tricuspi- 
datum. 

were  not  common  in  the  Carboniferous  forests.     The  scars 

in  fossil  or  recent  tree-ferns  are  many  times  larger  thar* 

12 


128  PALEOZOIC   TIME. 

those  of  Lepidodendra,  and  the  fossils  may  be  thus  distin- 
guished. 

(2.)  Lycopodium  tribe. — The  Lepidodendra  appear  to  have 
been  among  the  most  abundant  of  Carboniferous  forest- 
trees,  especially  in  the  earlier  half  of  the  Carboniferous 
Age,  or  to  the  middle  of  the  Coal  Period.  They  probably 
covered  both  the  marshes  and  the  drier  plains  and  hills. 
Some  of  the  old  logs  now  preserved  in  the  strata  arc  50  to 
60  feet  in  length;  and  the  pine-like  leaves  were  occasionally 
a  foot  or  more  long.  The  taller  tree  to  the  left,  in  figure 
220,  is  a  Lepidodendron.  Figure  221  shows  the  surface- 
markings  of  one  of  the  species,  natural  size :  the  regular 
arrangement  of  the  scars  resembles  a  little  the  arrangement 
of  scales  on  a  fish,  and  this  gave  origin  to  the  name  Lepido- 
dendron, from  the  Greek  lepis,  scale,  and  dendron,  tree. 

(3.)  Equisetum  tribe. — Fig.  225  represents  a  portion  of  one 
of  the  tree-rushes,  or  Calamites,  usually  regarded  as  of  the 
Equisetum  tribe.  The  species  were  evidently  very  abundant 
in  the  great  marshes,  through  the  whole  of  the  Carbonif- 
erous Age ;  some  were  20  feet  or  more  high,  and  10  or  12 
inches  in  diameter. 

Besides  these  Ciyptogams  there  were  also  Fungi,  or  Mush- 
rooms; but,  as  already  stated,  no  remains  of  Mosses  from  the 
rocks  of  the  age  are  known. 

II.  PHENOGAMS,  or  Flowering  Plants,  Order  of  GYMNO- 
SPERMS. 

(1.)  Conifers. — Trunks  of  trees,  supposed  to  be  Coniferous 
in  character,  and  related  especially  to  the  Araucarian  pines, 
are  common.  As  stated  on  p.  109,  they  may  be  the  trunks 
of  Sigillarids ;  yet  this  is  not  probable. 

(2.)  Sigillarids. — The  Sigillarice  were  a  very  marked  fea- 
ture of  the  great  jungles  and  damp  forests  of  the  Coal  period. 
They  grew  to  a  height  sometimes  of  30  to  60  feet ;  but  the 
trunks  were  seldom  branched,  and  must  have  had  a  stiff, 
clumsy  aspect,  although  covered  above  with  long,  slender, 


CARBONIFEROUS   AGE  129 

rush-like  leaves.  Fig.  222  represents  a  common  species, 
exhibiting  the  usual  arrangement  of  the  scars  in  vertical 
lines,  and  also  indicating,  by  the  difference  in  the  scars  of 
the  right  row  from  those  of  the  others,  the  difference  of 
form  on  the  inside  and  outside  of  the  bark. 

(3.)  Stigmarice. — The  fossil  Stigmarice  are  stout  stems, 
generally  2  to  3  or  more  inches  thick,  having  over  the  sur- 
face distant  rounded  punctures  or  depressions. 

Fig.  223  is  a  portion  of  the  extremity  of  a  stem,  showing 
the  rounded  depressions  and  also  the  leaf-like  appendages 
occasionally  observed.  The  stems  or  branches  are  a  little 
irregular  in  form,  and  sparingly  branched.  They  have  been 
found  spreading,  like  roots,  from  the  base  of  the  trunk  of  a 
Siyillaria,  and  sometimes  also  from  that  of  a  Lepidodendron ; 
and  they  are  hence  regarded  either  as  the  roots  or  sub- 
aqueous stems  of  these  trees.  They  are  an  exceedingly 
common  fossil,  especially  in  the  under-clays  of  the  Coal 
measures  (p.  122).  If  they  are  roots,  they  indicate  that  the 
under-clay,  as  stated  by  Logan,  was  the  old  dirt-bed  in  which 
the  vegetation  that  gave  rise  to  a  bed  of  coal  first  took  root. 
If  subaqueous  stems,  as  Lesquereux  believes  them  to  have 
often  been,  they  grew  rind  spread  through  the  shallow 
waters,  and  formed  the  basis  of  floating  vegetation,  while 
the  clay  was  accumulating  over  the  bottom,  like  the  fire- 
clay beneath  a  modern  peat-bed. 

In  the  Carboniferous  landscape,  fig.  220,  p.  126,  the  broken 
trunk  to  the  right  is  a  Sigillaria.  The  landscape,  to  be  quite 
true  to  nature,  should  have  been  made  up  largely  of  Sigil- 
larice,  Catamites,  and  Lepidodendra,  with  few  tree-ferns.  The 
Stigmariffl  would  have  been  mostly  concealed  beneath  the 
water  or  soil,  or  in  the  submerged  mass  of  the  floating  islands 

(4.)  Fruits. — Besides  the  leaves,  stems,  and  trunks  already 
alluded  to,  there  are  various  nut-like  fruits  found  in  the 
Carboniferous  strata.  One  is  represented  in  fig.  226,  tho 
figure  to  the  left  being  that  of  the  shell,  and  the  other  that 


130  PALEOZOIC   TIME. 

of  the  nut  which  it  contained.  Some  of  them  are  two  inches 
in  length.  The  most  of  them  were  probably  the  fruit  of 
Sigillarice  or  Conifers;  some,  perhaps,  of  the  Lepidodendra. 

(5.'    Conclusions. — It  is  seen  from  the  above  that — 

(1.)  The  vegetation  of  the  Carboniferous  age  consisted 
very  largely  of  Cryptogams,  or  flowerless  plants. 

(2.)  The  flowering  plants,  or  Phenogams,  associated  with 
the  flowerless  vegetation,  were  of  the  order  of  Gymno- 
sperms,  whose  flowers  are  incomplete  and  inconspicuous. 

(3.)  While,  therefore,  there  was  abundant  and  beautiful 
foliage  (for  no  foliage  exceeds  in  beauty  that  of  Ferns),  the 
vegetation  was  nearly  flowerless. 

(4.)  The  characteristic  Cryptogams  were  not  only  of  the 
highest  group  of  that  division  of  plants,  but  in  general  they 
exceeded  in  size  and  perfection  the  species  of  the  present 
day,  many  being  forest-trees. 

2.  Animals. 

The  principal  steps  of  progress  in  animal  life  have  already 
been  in  part  pointed  out, — viz.  the  increase  in  the  variety 
and  number  of  land-Articulates;  there  being  Myriapods  (or 
Centipedes)  and  Scorpions,  as  well  as  Insects;  and  the  rise  in 
Vertebrates  from  water- Vertebrates,  or  Fishes,  to  Reptiles. 

1.  Radiates. — Among  Eadiates,  species  of  Crinoids  were 
especially  numerous  and  varied  in  form  in  the  Subcarbonif- 
erous  period.    Figs.  227  to  229  represent  some  of  the  species. 
The  radiating  arms  are  perfect  in  fig.  227,  but  wanting  in  228. 
Fig.  229  is  a  species  of  the  genus  Pentremites  (named  from  the 
Greek  pente,  five,  alluding  to  the  five-sided  form  of  the  fossil). 
The  Pentremites  had  a  long  stem  made  of  calcareous  disks, 
like  other  Crinoids,  but  no  long  radiating  arms  at  top. 

Fig.  230  presents  an  upper  view  of  a  very  common  Coral 
of  the  same  period :  it  has  a  columnar  appearance  in  a  side 
view. 

2.  Mollusks. — The  tribe  of  Bryozoans  contained  the  sin- 


CARBONIFEROUS   AGE. 


131 


gular  screw-shaped  (or  auger-shaped)  coral  shown  in  fig.  231 
and  named  Archimedes  (referring  to  Archimedes'  screw).    It 


Figs.  227-237. 


RADIATES:  Fig.  227,  Zeaerinus  elegans;  22S,  Actinocrinus  proboscidialis ;  229,  Pentremiteg 
pyriformis ;  230,  Li  thostrot  ion  Canadense. — MOLLCSES  :  Fig.  231,  Archimedes  reversa ;  232, 
Clionetes  mescloba;  233,  Productus  Rogersi;  234,  Spirifer  cameratus;  235,  Athyris  sub- 
tilita;  236,  Pleurotomaria  tabulata;  237,  Pupa  vetusta. 

is  made  up  of  minute  cells  that  open  over  the  lower  surface; 

each  of  the  cells,  when  alive,  contained  a  minute  Brjozoan 

12* 


132 


PALEOZOIC   TIME. 


(p.  57).  These  fossils  are  common  in  some  of  the  Subcar- 
boniferous  limestone  strata. 

Brachiopods  were  the  most  abundant  of  Mollusks  through 
the  Carboniferous  age,  and  especially  species  of  the  genera 
Spirifer  and  Productus.  Figures  232 -to  235  are  of  species 
from  the  American  Coal  measures:  fig.  234,  a  Spirifer;  fig. 
233,  a  Productus;  fig.  232,  a  Chonetes;  fig.  235,  an  Athyris, 
occuring  also  in  Europe.  Fig.  236  represents  one  of  the 
Gasteropods  of  the  Coal  measures.  Fig.  237  is  a  Pupa,  the 
first  yet  known  of  land-snails :  it  is  from  the  Coal  measures 
of  Nova  Scotia.  The  order  of  Cephalopods  contained  but 
few  and  small  species  of  the  old  tribe  of  Orthocerata,  but 
many  of  the  Ammonite-like  Goniatites. 

3.  Articulates. — Among  Articulates,  Crustaceans  appeared 
under  a  new  form,  much  like  that  of  modern  shrimps  (fig. 
238,  from  Scotland),  and  Trilobites  were  of  rare  occurrence. 

Figs.  238-240. 


CRUSTACEAN:  Fig.  238,  Anthracopalaamon  Salteri.— MTRIAPOD:   Fig.  239  a,  Xylobius  Sigil- 
larue.— INSECT-WISG  :  Fig.  240,  Blattina  venusta. 

Fig.  239  represents  a  Myriapod  resembling  a  modern 
lulus,  from  Nova  Scotia ;  239  a,  shows  the  organs  of  the 
mouth,  as  they  are  still  preserved  in  the  specimen. 

Fig.  240  is  a  wing  of  an  Insect  of  the  genus  Blattina, 


CARBONIFEROUS    AGE. 


133 


related  to  the  modorn  Cockroach  (or  Blatta),  drawn  from  a 
specimen  obtained  in  the  Coal  measures  of  Arkansas.  There 
were  also  species  of  Neur apterous  insects,  of  Locusts  (or 
Orthopterous  insects)  and  Beetles  (or  Coleopters),  besides 
Scorpions  (of  the  class  of  Spiders). 

4.  Vertebrates. — Fishes  were  numerous,  both  of  the  orders 
of  Ganoids  and  Selachians.  All  the  Ganoids  were  of  the 
ancient  type,  having  the  caudal  fin  vertebrated  (or  hetero- 
cercal),  as  in  the  Palceoniscus,  represented  in  fig.  241,  a  Per- 
mian species.  Many  of  the  Selachians,  or  Sharks,  were  of 
great  size,  as  shown  by  the  fin-spines.  Fig.  242  represents 
a  small  portion  of  one  of  these  spines,  natural  size,  from 
the  Subcarboniferous  beds  of  Europe.  One  of  the  largest 
specimens  of  the  same  species  thus  far  found  had  a  length 


Figs.  241,  242. 


Fig.  241,  Palaeoniscus  Freieslebeni  (X  l/Q  ;  242,  Part  of  a  spine  of  Ctenacanthus  major. 

of  14£  inches,  and  when  entire  it  must  have  been  full  18 
inches  long. 


134 


PALEOZOIC   TIME. 


The  first  traces  of  Keptiles  yet  known  occur  in  the  Sub- 
carboniferous  beds  of  Pottsville,  Pennsylvania. 

Figs.  243-245. 


Fig.  243,  Tracks  of  Sauropus  primaevus  (XVs):   "*&*>  Raniceps  Lyellu;  245  a,  Vertebra  01 
Eosaurus  Acadianui. 


CARBONIFEROUS   AGE.  135 

Fig.  243  is  a  reduced  sketch  of  a  slab  containing  tracks 
of  the  species,  and  also  an  impression  left  by  the  tail  of  the 
animal.  The  tracks  of  the  fore-feet,  as  described  by  I.  Lea, 
are  5-fingered  and  4  inches  broad,  and  those  of  the  hind 
feet  4-fingered  and  nearly  of  the  same  size;  while  the  stride 
indicated  was  13  inches.  Fig.  244  represents  a  skeleton  of 
an  Amphibian  from  the  Ohio  Coal  measures,  found  by  New- 
berry  j  and  fig.  245  a  vertebra  of  a  swimming  Saurian 
probably  related  to  the  Enaliosaurs,  or  Sea-Saurians,  of  the 
Mcsozoic  (see  p.  180),  discovered  by  Marsh  in  the  Coal 
measures  of  Nova  Scotia.  This  vertebra  is  concave  on  both 
surfaces,  as  shown  in  the  section  in  fig.  245  a,  and  in  this 
respect  resembles  those  of  fishes.  The  Enaliosaurs  had 
paddles  like  "Whales. 

These  Enaliosaurs,  or  swimming  Eeptiles,  are  the  highest 
species  of  animal  yet  discovered  in  rocks  of  the  Carbonif- 
erous period.  In  the  Permian  period  there  were  still  higher 
Reptiles,  called  Thecodonts  (because  the  teeth  are  set  in 
sockets,  from  the  Greek  theca,  case,  and  odous,  tooth).  But 
these  also  had  the  fish-like  characteristic  of  doubly-concave 
vertebra,. 


5.  General  Observations. 

1.  Formation  of  Coal  and  the  Coal  measures.—  (1.)  Origin  of 
the  Coal.  —  The  vegetable  origin  of  coal  is  proved  by  the  fol- 
lowing facts  :  — 

(1.)  Trunks  of  trees,  retaining  still  the  original  form  and 
part  of  the  structure  of  the  wood,  have  been  found  changed 
to  mineral  coal,  both  in  the  Carboniferous  and  more  modern 
formations,  showing  that  the  change  may  and  does  take 
place. 

(2.)  Beds  of  peat,  a  result  of  vegetable  growth  and  accu- 
mulation, exist  in  modern  marshes;  and  in  some  cases  they 
are  altered  below  to  an  imperfect  coal  (see  page  263  on  the 
formation  of  peat). 


136 


PALEOZOIC   TIME. 


(3.)  Remains  of  plants,  their  leaves,  branches,  and  stems 
or  trunks,  abound  in  the  Coal  measures ;  trunks  sometimes 
extend  upward  from  a  coal-bed  into  and  through  some  of 
the  overlying  beds  of  rock ;  roots  or  stems  abound  in  the 
under-elays. 

(4.)  The  hardest  anthracite  contains  throughout  its  mass 
vegetable  tissues.  Prof.  Bailey  examined  with  a  high  mag- 
nifying power  several  pieces  of  anthracite  burnt  at  one  end, 
like  fig.  246,  taking  fragments  from  the  junction  of  the 
white  and  black  portion,  and  detected  readily  the  tissues. 
Figure  247  represents  the  ducts,  as  they  appeared  in  one 
case  under  his  microscope ;  and  fig.  248  part  of  the  same, 
more  magnified. 

(2.)  Decomposition  of  Vegetable  Material. — Carbon,  the  essen- 
tial element  of  mineral  coal,  exists  as  one  of  the  constituents 
of  all  wood  or  vegetable  material,  making  up  49  per  cent, 
(or  nearly  one-half)  of  dry  wood ;  and  to  obtain  this  carbon 
as  coal  it  is  necessary  only  to  expel  the  other  constituents 


Figs.  246-248. 


of  the  wood, — that  is,  the  gases  oxygen  and  hydrogen.  Vege- 
table matter  decomposing  in  the  open  air — like  wood  burnt 
in  an  open  fire — passes,  carbon  and  all,  into  gaseous  combi- 
nations, and  little  or  no  carbon  is  left  behind.  But  when  it 
is  decomposed  slowly  under  water,  or  by  a  slow,  half- 
smothered  fire,  only  part  of  the  carbon  is  lost  in  gaseous 


CARBONIFEROUS   AGE.  137 

combinations,  the  rest  remaining  as  coal, — called  mineral 
coal  in  the  former  case,  and  charcoal  in  the  latter. 

The  actual  loss,  by  weight,  in  the  transformation  into 
bituminous  coal,  is  at  least  three-fourths  of  the  wood,  and  in 
that  into  anthracite,  five-sixths.  Adding  to  this  loss  that 
from  compression,  by  which  the  material  is  brought  to  the 
density  of  mineral  coal,  the  whole  reduction  in  bulk  is  not 
less  than  seven-eighths  for  the  former,  and  eleven-twelfths  for 
the  latter.  In  other  words,  it  would  take  8  feet  of  vegetable 
matters  to  make  1  of  bituminous  coal,  and  12  feet  to  make 
1  of  anthracite. 

(3.)  Impurities  in  Coal. — The  coal  thus  formed  contains 
the  silica  existing  in  minute  quantities  in  vegetable  sub- 
stances, and  also  other  earthy  materials  that  are  not  carried 
away  in  solutions.  By  this  means,  and  through  the  addition 
of  clay  or  earth,  introduced  by  waters  or  by  the  winds,  the 
coal  has  derived  the  earthy  impurities  which  give  rise  to  the 
ashes  and  slag  formed  in  a  hot  fire. 

(4.)  Accumulation  and  Formation  of  Coal-beds. — The  origin 
of  coal-beds  was,  then,  as  follows : — The  plants  of  the  great 
marshes  and  shallow  lakes  of  the  Coal  era,  the  latter  with 
their  floating  islands  of  vegetation,  continued  growing  for  a 
long  period,  dropping  annually  their  leaves,  and  from  time 
to  time  decaying  stems  or  branches,  until  a  thick  accumula- 
tion of  vegetable  remains  was  formed, — probably  8  feet  in 
thickness  for  a  one-foot  bed  of  bituminous  coal,  or  over  60 
feet  for  such  a  bed  as  that  of  the  Pittsburg  region  (p.  123). 
The  bed  of  material  thus  prepared  over  the  vast  wet  areas 
of  the  continent  early  commenced  to  undergo  at  bottom 
that  slow  decomposition  the  final  result  of  which  is  mineral 
coal.  But,  as  the  coal-beds  alternate  with  sandstones,  shales, 
conglomerates,  and  limestones,  the  long  period  of  verdure 
was  followed  by  another  of  overflowing  waters, — and  gene- 
rally oceanic  waters,  as  the  fossils  prove, — which  carried 
sands,  pebbles,  or  earth  over  the  old  marsh,  till  scores  or 


138  PALEOZOIC   TIME. 

hundreds  ol  feet  in  depth  of  such  deposits  had  been  made. 
Thus,  the  bed  of  vegetable  debris  was  buried  where  the 
process  of  decomposition  proper  for  making  coal  could  still 
go  on  to  its  completion ;  for  it  would  have  the  smothering 
influence  of  the  burial,  as  well  as  the  presence  of  water,  to 
favor  the  process. 

(5.)  Climate  of  the  Age. — The  wide  distribution  of  the  coal 
regions  over  the  globe,  from  the  tropics  to  the  remote 
Arctic,  and  the  general  similarity  of  the  vegetable  remains 
in  the  coal-beds  of  these  remote  zones,  prove  that  there  was 
a  general  uniformity  of  climate  over  the  globe  in  the  Car- 
boniferous age,  or  at  least  that  the  climate  was  nowhere 
colder  than  warm-temperate.  Similar  corals  and  shells  ex- 
isted during  the  Subcarboniferous  period  in  Europe,  the 
United  States,  and  the  Arctic  within  20°  of  the  north  pole, 
and  so  profusely  as  to  form  thick  limestones  out  of  their 
accumulations.  The  ocean's  waters,  even  in  the  Arctic, 
were,  therefore,  warm  compared  with  those  of  the  modern 
temperate  zone,  and  probably  quite  as  warm  as  the  coral- 
reef  seas  of  the  present  age,  which  lie  mostly  between  the 
parallels  of  28°  either  side  of  the  equator. 

(6.)  Atmosphere. — The  atmosphere  was  especially  adapted 
for  the  age  in  other  respects.  It  contained  a  larger  amount 
than  now  of  carbonic  acid  gas, — the  gas  which  promotes  (if 
not  in  excess)  the  growth  of  vegetation.  Plants  derive 
their  carbon  mainly  from  the  carbonic  acid  of  the  atmo- 
sphere ;  and  hence  the  mineral  coal  of  the  world  is  approxi- 
mately a  measure  of  the  amount  of  carbonic  acid  the  atmo- 
sphere in  the  Carboniferous  era  lost.  The  growth  of  the  flora 
of  that  age  was  a  means  of  purifying  the  atmosphere  so  as 
to  fit  it  for  the  higher  terrestrial  life  that  was  afterwards  to 
possess  the  world. 

Again,  the  atmosphere  was  more  moist  than  now.  This 
follows  from  the  greater  heat  of  the  climate  and  the 
greater  extent  as  well  as  higher  temperature  of  the  oceans. 


CARBONIFEROUS   AGE.  139 

The  continents,  although  large  during  the  intervals  of  ver- 
dure compared  with  the  areas  above  the  ocean  in  the  Devo- 
nian or  Silurian,  were  still  small  and  the  land  low.  It  must, 
therefore,  have  been  an  era  of  prevailing  clouds  and  mists. 
A  moist  climate  would  not,  however,  have  been  universal, 
as  even  the  ocean  has  now  its  great  areas  of  drought 
depending  on  the  courses  of  the  winds.  America  is  now 
the  moist  forest-continent  of  the  globe;  and  the  great 
extent  of  the  coal-fields  of  its  northern  half  proves  that  it 
bore  the  same  character  in  the  Carboniferous  age. 

2.  Geography. — (1.)  Appalachian  and  Rocky  Mountains  not 
made. — On  page  116  it  is  stated  that  the  continents  in  this 
age  were  low,  with  few  mountains.  The  non-existence  of 
the  Appalachians  of  Pennsylvania  and  Virginia  is  proved 
by  the  fact  that  the  rocks  of  these  mountains  are  to  a  con- 
siderable extent  Carboniferous  rocks ; — partly  marine  rocks, 
indicating  that  the  sea  then  spread  over  the  region  where 
they  now  lie ;  partly  coal-beds,  each  bed  evidence  that  a 
great  fresh-water  marsh,  flat  as  all  marshes  are,  for  a  long 
while  occupied  the  region  of  the  present  mountains. 

There  is  the  same  evidence  that  the  mass  of  the  Eocky 
Mountains  had  not  been  lifted;  for  marine  Carboniferous 
rocks  constitute  a  large  part  of  these  mountains,  many 
beds  containing  remains  of  the  life  of  the  Carboniferous  seas 
that  covered  that  part  of  North  America.  Only  islands,  or 
archipelagos  of  islands,  made  by  some  Azoic  and  Paleozoic 
ridges,  existed  in  the  midst  of  the  wide-spread  western 
waters. 

(2.)  Condition  in  the  Subcarboniferous  Period. — Through  the 
first  period  of  this  age — the  Subcarboniferous — the  continent 
was  almost  as  extensively  beneath  the  sea  as  in  the  Devo- 
nian age.  This,  again,  is  shown  by  the  nature  and  extent 
of  the  Subcarboniferous  rocks, — the  great  crinoidal  lime- 
stones. The  shallow  continental  seas  were  profusely  planted 
with  Crinoids  amid  clumps  of  Corals.  Brachiopods  were  here 

13 


140  PALEOZOIC   TIME. 

and  there  in  great  abundance,  many  lying  together  in  beds 
as  oysters  in  an  oyster-bed ;  other  Mollusks,  both  Conchi- 
fers  and  Gasteropods,  were  also  numerous;  Trilobites  were 
few ;  Goniatites  and  Nautili,  along  with  Ganoid  Fishes  and 
sharks,  were  the  voracious  life  of  the  seas,  and  Amphi- 
bian reptiles  haunted  the  marshes. 

(3.)  Transition  to  the  Carboniferous  Period. — Finally,  the 
Subcarboniferous  period  closed,  and  the  Carboniferous 
opened.  But  in  the  transition  from  the  period  of  submerg- 
ence to  that  of  emergence  required  to  bring  into  existence 
the  great  marshes,  a  wide-spread  bed  of  pebbles,  gravel,  and 
sand  was  accumulated  by  the  waves  dashing  rudely  over 
the  surface  of  the  rising  continent;  and  these  pebble-beds 
make  the  Millstone  grit  that  marks  the  commencement  of  the 
Carboniferous  period  in  a  large  part  of  eastern  North  Ame- 
rica, especially  along  the  Appalachian  region,  and  also  in 
Europe. 

(4.)  Coal-plant  Areas  in  the  Carboniferous  Period. — Then 
began  the  epoch  of  the  Coal  measures. 

The  positions  of  the  great  coal  areas  of  North  America 
(see  map,  p.  69)  are  the  positions,  beyond  question,  of  the 
great  marshes  and  shallow  fresh-water  lakes  of  the  period. 
But  it  is  probable  that  the  number  of  these  marshes  was  less 
than  that  of  the  coal  areas.  The  Appalachian,  Illinois,  Mis- 
souri, Arkansas,  and  Texas  fields  may  have  made  one  vast 
Interior  continental  marsh-region,  and  those  of  Khode  Island, 
Nova  Scotia,  and  New  Brunswick  an  Eastern  border  marsh- 
region.  There  is  some  reason,  however,  for  believing  that 
a  low  area  of  dry  land  (or  not  marshy  land),  extending 
from  the  region  of  Cincinnati  into  Tennessee,  divided  the 
Interior  marsh,  or  at  least  its  northern  portion. 

The  Michigan  marsh-region  appears  also  to  have  had  its  dry 
margins,  instead  of  coalescing  with  the  Illinois  or  Ohio  areas. 

It  is  not  to  be  inferred  that  the  marshes  alone  were 
covered  with  verdure.  The  vegetation  probably  spread  over 


CARBONIFEROUS   AGE.  141 

all  the  dry  land,  though  making  thick  deposits  of  vegetable 
remains  only  where  there  were  marshes  under  dense  jungle 
growth  and  shallow  lakes  with  their  floating  islands. 

(5.)  Alternations  of  Condition,  Changes  of  Level. — It  has 
been  remarked  that  the  many  alternations  of  the  coal- 
beds  with  sandstones,  shales,  conglomerates,  and  lime- 
stones (p.  117),  are  evidence  of  as  many  alternations  of 
level  during  the  era.  After  the  great  marshes  had  been 
long  under  verdure,  the  ocean  began  again  to  encroach  upon 
them,  and  finally  swept  over  the  whole  surface,  destroying 
the  land  and  fresh-water  life  of  the  area, — that  is,  the  land 
and  fresh-water  Plants,  Mollusks,  Insects,  and  Reptiles, — but 
distributing  at  the  same  time  the  new  life  of  the  salt  waters. 
Then,  after  another  long  period  of  various  oscillations  in 
the  water-level,  in  which  sedimentary  beds  in  many  alter- 
nations were  formed,  the  continent  again  rose  to  aerial  life, 
and  the  marshes  and  shallow  lakes  were  luxuriant  anew 
with  the  Carboniferous  vegetation.  Thus  the  sea  prevailed 
at  intervals — intervals  of  long  duration — through  the  era 
even  of  the  Coal  measures ;  for  the  associated  sedimentary 
beds,  as  has  been  stated,  are  at  least  fifty  times  as  thick  as 
the  coal  beds. 

These  oscillations  continued  until  3000  to  4000  feet  of 
strata  were  formed  in  Pennsylvania,  and  over  14,000  in 
Nova  Scotia. 

The  Carboniferous  period  was,  therefore,  ever  varying 
in  its  geography.  A  map  of  its  condition  when  the  great 
coal  beds  were  accumulating  would  have  its  eastern  coast- 
line not  far  inside  of  the  present,  and  in  the  region  of  Nova 
Scotia  and  New  England  even  outside  of  the  present.  The 
southern  coast-line  would  pass  through  central  Carolina, 
Georgia,  and  Alabama,  and  northern  Mississippi,  then,  west 
of  the  Mississippi,  around  Arkansas  and  the  bordering  coun- 
ties of  Texas ;  thence  it  would  stretch  northward,  bounding 
a  sea  covering  a  large  part  of  the  Eocky  Mountain  region, 


142  PALEOZOIC    TIME. 

for  the  Coal  period  was  in  that  part  of  the  continent 
mainly  a  time  of  limestone-making.  But  in  a  map  repre- 
senting it  during  the  succeeding  times  of  submergence,  the 
coast-line  would  run  through  south  middle  New  England, 
then  near  the  southern  boundary  of  New  York  State, 
then  northwestward  around  Michigan,  then  southward 
again  to  northern  Illinois,  and  then  westward  and  north- 
westward to  the  Upper  Missouri  region,  or  the  Eocky 
Mountain  sea.  Through  these  conditions,  as  the  extremes, 
the  continent  passed  several  times  in  the  course  of  the  Car- 
boniferous period. 

(6.)  Condition  in  the  Permian  Period. — Finally,  in  the 
Permian  period,  the  Appalachian  region,  and  the  Interior 
region  east  of  a  north-and-south  line  running  through  Mis- 
souri, appear  to  have  been  mainly  above  the  ocean;  for  the 
Permian  beds  are  mostly  confined  to  the  meridian  of  Kansas 
and  the  remoter  "West. 

GENERAL  OBSERVATIONS  ON  THE  PALEOZOIC. 

1.  Rocks. — (1.)  Maximum  thickness. — The  maximum  thick- 
ness of  the  rocks  of  the  Silurian  age  in  North  America  is 
22,000  feet;  of  the  Devonian,  about  14,000  feet;  and  of  the 
Carboniferous  age,  under  15,000  feet. 

(2.)  Diversities  of  the  different  Continental  regions  as  to 
kinds  of  rocks. — The  Paleozoic  rocks  of  the  Appalachian 
region  are  mainly  sandstones,  shales,  and  conglomerates; 
only  about  one-fourth  in  thickness  of  the  whole  consists  of 
limestone.  The  rocks  of  the  Interior  continental  are  mostly 
limestone,  full  two-thirds  being  of  this  nature. 

The  difference  of  these  two  regions,  in  this  particular, 
will  be  appreciated  on  comparing  the  following  general  sec- 
tion of  the  strata  of  the  Interior  with  the  section,  on  page 
66,  of  the  rocks  of  New  York, — New  York  State  lying  on 
the  inner  borders  of  the  Appalachian  region.  The  Lower 
Silurian  beds  in  the  Mississippi  basin,  as  the  section  shows, 


GENERAL   OBSERVATIONS. 


143 


consist  mainly  of  limestones;  so  also  the  Upper  Silurian, 
Devonian,  and  Subcarboniferous  formations;  and  the  Car- 
boniferous of  the  region  contains  more  limestone  than  that 
of  the  East.  In  the  Devonian  of  the  Interior,  a  black  shale, 
one  or  two  hundred  feet  thick,  is  the  only  representative  of 
the  Hamilton  group ;  and  a  few  hundred  feet  of  sandstone 
— part  of  the  so-called  Waverly  sandstone — corresponds  to 
the  Chemung  group,  or  Uppermost  Devonian. 

In  the  Eastern  border  region,  about  the  Gulf  of  St.  Law- 
rence, there  is  a  great  predominance  of  limestones  in  the 


Fig.  249. 


PERMIAN 


CARBOXIFEROCS 


SCBCARBONIFEROUS 
(HAMILTON 

lu.  HELDERBERG.... 

NIAGARA 

HUDSON  RIVER 

TRENTON. -J 

POTSDAM 


Coal  Conglomerate. 
Subcarboniferous  limestone. 


VTaverly  sandstone  (=  Chemung 
and  Subcarboniferous). 


limestone  and  shale. 

Trenton  limestone;  Galena  lime- 
stone ;  Black  River  limestone. 

Lower  magnesian  limestone  ( = 
Calciferous). 


Section  of  the  Paleozoi 


formations.  They  prove  the  existence  in  that  region  of  an 
Atlantic  border  basin  similar  in  some  respects  to  the  basin 
of  the  Interior,— the  two  being  separated  by  the  northern 
part  of  the  Appalachian  region. 

(3  )  Diversities  of  the  Appalachian  and  Interior  Continental 
regions  as  to  the  thickness  of  the  rocks.-ln  the  Appalachian 

13* 


144  PALEOZOIC   TIME. 

region  the  maximum  thickness  of  the  Paleozoic  rocks  is 
about  50,000  feet.  But  this  thickness  is  not  observed  at 
any  one  locality,  it  being  obtained  by  adding  together  the 
greatest  thicknesses  of  the  several  formations  wherever 
observed.  The  greatest  actual  thickness  at  any  one  place  in 
Pennsylvania  is  about  36,000  feet,  or  between  6i  and  7  miles. 

In  the  central  portions  of  the  Interior  continental  region, 
the  thickness  varies  from  3500  feet  (and  still  less  on  the 
northern  border)  to  6000  feet;  and  it  is,  therefore,  from 
one-sixth  to  one-tenth  that  in  the  Appalachian  region. 

(4.)  Origin  of  the  deposits. — The  frag  mental  rocks,  as  those 
of  sand,  clay,  mud,  pebbles  (or  the  sandstones,  shales, 
earthy  sandstones  and  conglomerates),  were  made  from  the 
wear  of  pre-existing  rocks  under  the  action  of  water.  The 
water  was  mainly  that  of  the  ocean,  and  the  power  was 
that  of  the  waves  and  currents.  The  material  acted  upon 
was  subjected  to  wave-action,  and  must  have  been  at  or 
near  the  surface.  The  material  of  the  coarser  rocks  may 
have  been  accumulating  where  the  waves  were  dashing 
against  a  beach  or  an  exposed  sand-reef,  or  else  where  cur- 
rents were  in  rapid  movement  over  the  bottom ;  for  accumu- 
lations of  pebbles  and  coarse  sand  are  now  made  under 
these  circumstances.  The  material  of  the  earthy  sandstones 
may  have  been  the  mud  or  earthy  sands  forming  the  bottom 
of  shallow  seas.  The  fine  clayey  or  earthy  deposits  must 
have  been  made  in  sheltered  bays  or  interior  seas,  in  which 
the  waves  were  light,  and,  therefore,  fitted  to  produce  by 
their  gentle  attrition  the  finest  of  mud  ;  or  else  in  the  deeper 
off-shore  waters,  where  the  finer  detritus  of  the  shores  is 
liable  to  be  borne  by  the  currents. 

Accumulations  of  any  degree  of  thickness  may  be  made 
in  shallow  waters,  provided  the  region  is  undergoing  very 
slow  subsidence ;  for  in  this  way  the  depth  of  the  waters 
may  be  kept  sufficient  to  allow  of  constantly  increasing 
depositions.  Thus,  by  a  slow  subsidence  of  1000  feet, 


GENERAL   OBSERVATIONS.  145 

deposits  1000  feet  thick  may  be  produced,  and  the  depth  of 
water  at  no  time  exceed  20  feet.  The  occurrence  of  ripple- 
marks,  mud-cracks,  or  rain-drop  impressions  in  many  beds 
of  most  of  the  formations,  proves  that  the  layers  so  marked 
were  successively  near  the  surface,  and,  therefore,  that  there 
must  have  been  a  gradual  sinking  of  the  bottom  as  the  beds 
were  formed. 

The  limestones  of  the  Paleozoic  were  probably  made,  in 
every  case,  out  of  organic  remains,  as  Shells,  Corals,  Crinoids, 
etc.,  and  perhaps  in  some  cases  (as  that  of  the  Lower  Mag- 
nesian  limestones  of  the  Interior)  out  of  minute  Rhizo- 
pods,  which  are  known  to  have  formed,  to  a  large  extent, 
the  chalk-beds  of  Europe.  Shells,  Corals,  and  Crinoids 
must  be  ground  up  by  the  waves  to  form  fine-grained  rocks ; 
while  the  shells  of  Rhizopods  are  so  minute  as  to  be  already 
fine  grains,  and  may  become  compact  rocks  by  simple  con- 
solidation. 

The  hornstone  in  the  limestones,  as  remarked  on  page  109, 
may  be  wholly  of  organic  origin. 

2.  Time-Ratios. — Judging  from  the  maximum  thickness  of 
the  rocks  of  the  several  Paleozoic  ages  in  North  America, 
and  allowing  that  five  feet  of  fragmental  rocks  may  accumu- 
late in  the  time  required  for  one  foot  of  limestone,  the  rela- 
tive lengths  of  the  Silurian,  Devonian,  and  Carboniferous 
ages  were  not  far  from  3:1:1,  and  the  Lower  Silurian  era 
was  four  times  as  long  as  the  Upper. 

Thus  time  moved  on  slowly  in  the  earth's  first  beginnings. 
The  condition  of  the  earth  in  an  age  of  Mollusks,  when 
only  Invertebrates  and  Sea-weeds  were  living, — when  all 
life  was  the  life  of  the  waters,  and  nothing  existed  above  the 
ocean's  level,— was  very  inferior  to  that  of  the  Carbonif- 
erous, when  the  continents  had  their  forests,  the  waters 
their  fishes,  and  the  marshes  their  reptiles.  Yet  the  length 
of  the  time  through  which  the  earth  was  groping  under 
the  first-mentioned  condition  was  at  least  three  times  that 


146  PALEOZOIC    TIME. 

under  the  last ;  and  the  earlier  Lower  Silurian  era  was  four 
times  as  long  as  the  Upper  Silurian.  Such  was  the  divine 
system  in  the  progress  of  creation.  Such  is  time  in  the 
view  of  the  infinite  Creator. 

3.  Geography. — (1.)  Close  of  Azoic  time. — The  map  on  page 
73  shows  approximately  the  outline  of  the  dry  land  of 
North  America  at  the  close  of  Azoic  time.  The  only  moun- 
tains were  Azoic  mountains,  the  principal  of  which  were 
the  Laurentian  of  Canada  and  the  Adirondack  of  northern 
New  York.  We  cannot  judge  of  the  height  of  these  moun- 
tains then  from  what  we  now  see,  after  all  the  ages  of 
Geology  have  passed  over  them,  for  the  elements  and  run- 
ning water  have  never  ceased  action  since  the  time  of  their 
uplift,  and  the  amount  of  loss  by  degradation  must  have 
been  very  great. 

(2.)  General  Progress  through  Paleozoic  time. — The  increase 
of  dry  land  during  the  Paleozoic  has  been  shown  (pp.  99, 
115)  to  have  taken  place  mainly  along  the  borders  of  the 
Azoic,  so  that  the  old  nucleus  has  been  on  the  gradual 
increase.  This  increase  is  well  marked  from  north  to  south 
across  New  York.  At  the  close  of  the  Lower  Silurian,  the 
shore-line  was  not  far  from  the  present  position  of  the 
Mohawk,  showing  but  a  slight  extension  of  the  dry  land  in 
the  course  of  this  very  long  era ;  when  the  Upper  Silurian 
ended,  the  shore-line  extended  along  15  or  20  miles  south  of 
the  Mohawk.  When  the  Devonian  ended  and  the  Carbonif- 
erous age  was  about  opening,  the  coast-line  was  just  north 
of  the  Pennsylvania  boundary.  Thus,  the  dry  part  of  the 
continent  was  on  the  slow  increase. 

The  progress  southward  was  at  an  equal  rate  in  Wis- 
consin, where  there  is  an  isolated  Azoic  region  like  that  of 
northern  New  York.  In  the  intermediate  district  of  Michi- 
gan, the  coast  made  a  deep  northern  bend  through  the  Silu- 
rian and  Devonian.  In  the  Carboniferous  the  same  great 
Michigan  bay  existed  during  the  intervals  of  submergence; 


GENERAL    OBSERVATIONS.  147 

but  it  was  changed  to  a  Michigan  marsh  or  fresh-water  lake, 
filled  with  Coal-measure  vegetation  during  the  intervening 
portions  of  the  Carboniferous  period;  and  at  the  same 
times,  as  explained  on  page  140,  the  continent  east  of  the 
western  meridian  of  Missouri  had  nearly  its  present  extent, 
though  not  its  mountains  or  its  rivers. 

(3.)  Regions  of  rock-making,  and  their  differences. — The  sub- 
merged part  of  the  continent  was  the  scene  of  nearly  all 
the  rock-making;  and  this  work  probably  went  on  over  its 
whole  wide  extent. 

The  rocks,  as  partially  explained  on  page  144,  varied  in 
kind  with  the  depth  and  with  the  exposure  to  the  open  sea. 

This  Interior  continental  region,  which  was  for  the  most  of 
the  time  a  great  interior  oceanic  sea,  afforded  the  conditions 
fitted  for  the  growth  of  corals  and  crinoids  and  other  clear- 
water  species,  and  hence  for  the  making  of  limestone  reefs 
out  of  their  remains ;  for  limestones  are  the  principal  rocks 
of  the  interior.  Yet  there  were  oscillations  in  the  level;  for 
there  are  abrupt  transitions  in  the  limestones,  and  some 
sandstones  and  shales  alternate  with  them.  But  these  oscil- 
lations were  not  great,  the  whole  thickness  of  the  rocks,  as 
stated  on  page  144,  being  small. 

The  Appalachian  region,  on  the  contrary,  presented  the 
conditions  required  for  fragmental  deposits.  It  was  ap- 
parently a  region  of  immense  sand-reefs  and  mud-flats, 
with  bays,  estuaries,  and  extensive  submerged  plateaus  or 
off-shore  soundings,  such  as  might  have  existed  in  the  face 
of  the  ocean.  Here,  too,  the  change  of  level  was  very  great; 
for  within  this  region  occur  the  6|  to  7  miles  of  Paleozoic 
formations  (p.  144),  and  even  9  miles,  reckoning  the  maxi- 
mum amount  of  all  the  deposits.  This  vast  thickness  indi- 
cates that  while  there  were  various  upward  and  downward 
movements  over  this  Appalachian  region  through  Paleozoic 
time,  the  downward  movements  exceeded  the  upward  even 
by  the  amount  just  stated.  These  movements,  moreover,  were 


148  PALEOZOIC   TIME. 

in  progress  from  the  Potsdam  period  onward;  the  forma- 
tions of  nearly  every  period  in  the  series  exceed  8  to  10 
times  the  thickness  they  have  over  the  Interior  region. 

(4.)  Mountains  of  Paleozoic  origin. — The  mountains  in 
eastern  North  America,  made  in  the  course  of  the  Paleozoic 
ages,  were  few.  Those  of  the  region  south  of  Lake  Supe- 
rior about  Keweenaw  Point,  and  to  the  west,  probably  rose 
during  the  latter  part  of  the  Potsdam  period.  The  Green 
Mountain  region  became  dry  land  after  the  Lower  Silurian 
(p.  91)  ;  but  there  is  no  reason  to  believe  that  it  was  very 
much  raised;  for  the  eastern  half  of  Vermont  \vas  beneath 
the  ocean,  and  became  covered  by  coral  reefs  and  other 
formations  during  the  Devonian  age.  The  Devonian  beds 
of  the  vicinity  of  Gaspe  may  have  been  raised  into  ridges 
before  the  Carboniferous  age  began.  But  the  larger  part 
of  the  continental  area  was  still  without  mountains.  The 
Eocky  chain  had  only  some  ridges  as  islands  in  the  seas, 
and  the  Appalachians  were  yet  to  be  made. 

(5.)  Rivers — Lakes. — The  depression  between  the  New 
York  and  the  Canada  Azoic,  dating  from  the  Azoic  age, 
was  the  first  indication  of  a  future  St.  Lawrence  channel. 
It  continued  to  be  an  arm  of  the  sea,  or  deep  bay,  through 
the  Silurian,  and  underwent  a  great  amount  of  subsidence 
as  it  received  its  thick  Canadian  formations.  After  the 
Silurian  age,  marine  strata  ceased  to  form,  indicating 
thereby  that  the  sea  had  retired ;  and  fresh  waters,  derived 
from  the  Azoic  heights  of  Canada  and  New  York,  probably 
began  their  flow  along  its  upper  portion,  and  emptied  into 
the  St.  Lawrence  Gulf  of  the  time  not  far  below  Montreal. 

The  raising  of  New  York  State  out  of  water  at  the  close 
of  the  Devonian  suggests  that  from  that  time  the  Hudson 
valley  was  a  stream  of  fresh  water.  The  valley  itself,  and 
its  continuation  north  as  the  Champlain  valley,  date  from 
the  close  of  the  Lower  Silurian. 

The  Mississippi  and  its  tributaries,  east  and  .west,  were 


GENERAL   OBSERVATIONS.  149 

not  in  existence  in  the  Paleozoic  ages.  In  the  intervals 
of  Carboniferous  verdure,  when  the  continent  was  emerged, 
the  Ohio  and  Mississippi  basin  were  regions  of  great 
marshes,  lakes,  and  bayous,  and  not  of  great  rivers;  for 
rivers  could  not  exist  without  a  head  of  high  land  to  supply 
water  and  give  it  a  flow. 

Lake  Superior  was  a  district  of  vast  rock-deposits  and 
extensive  igneous  eruptions  in  the  Potsdam  period,  or  near 
the  close  of  that  period,  as  well  as  in  the  closing  Azoic ;  and 
the  thick  accumulations  show  that  deep  subsidences  were 
then  in  progress  there,  as  also  in  the  region  of  the  St. 
Lawrence;  so  that  we  may  infer  that  the  basin  of  this 
great  lake  was  already  in  process  of  formation  before  the 
Lower  Silurian  closed.  The  extent  and  position  of  the  great 
Michigan  bay  through  the  Silurian  and  Devonian  ages  and 
much  of  the  Carboniferous,  as  mentioned  on  pp.  99,  142, 
show  that  Lakes  Erie,  Huron,  and  Michigan  were  then 
within  the  limits  of  this  bay.  Whether  deeper  or  not  than 
other  portions  of  the  bay,  is  not  known. 

Thus,  Geology  studies  the  Geography  of  the  Paleozoic 
ages,  and  traces  North  America  through  its  successive 
stages  of  growth. 

4.  Climate. — No   evidence   has   been   found   through   the 
Paleozoic  records  of  any  marked  difference  of  temperature 
between  the  zones.     In  the  Carboniferous  age  the  Arctic 
seas  had  their  Corals  and  Brachiopods,  and  the  Arctic  lands 
their  forests  and  marshes  under  dense  foliage,  no  less  than 
those  of  America  and  Europe.     The  facts  on  this  subject 
are  stated  on  p.  138. 

5.  Life. — (1.)  Appearance  and  disappearance  of  species. — 
With  each  new  period  in  the  progressing  ages,  new  living 
species  were  introduced ;  and,  as  each  period  ended,  the  old 
more  or  less  completely  passed  away,  or  were  exterminated. 
There  were  also  partial  destructions  attending  the  many 
minor  changes  in  the  rock-formations,  as  in  the  transition 


150 


PALEOZOIC    TIME. 


from  the  formation  of  a  bed  of  shale  to  that  of  sandstone 
or  of  limestone,  or  the  reverse ;  and  some  new  species  made 
their  appearance  with  each  new  stratum.  Thus,  destruc- 
tions and  creations  took  place  at  intervals  through  the 
whole  course  of  the  ages. 

(2.)  The  exterminations  indicated  not  in  harmony  with  any 
development-theory. — This  extermination  of  the  life  of  a 
period  or  epoch,  according  to  the  evidence  gathered  from 
the  rocks,  cut  short  not  only  species,  but  genera,  families,  and 
tribes;  and  yet  these  same  genera  and  tribes  were  often 
begun  again  by  other  species,  and  so  continued  on.  Had 
the  system  of  creation  been  dependent  on  the  development 
of  species  from  species,  this  would  have  been  impossible.  The 
system  could  not  have  withstood  the  disasters  it  had  to 
encounter. 

(3.)  Beginning  and  ending  of  genera,  families,  and  higher 
groups.— The  following  table  of  the  tribe  of  Trilobites  illus- 
trates the  general  character  of  the  progress  which  took 
place  in  this  and  other  groups  : — 


TROOBITES.., 


Paradoxides,  Conocephalus,  Sao,  Ellipso- 
cephalus,  Hydrocephalus,  Dicelloce- 
phalus,  Arionellus,  Mcnocephalus,  Ba- 
thyurus.. 


01  en  us  and  Agnostus.. 
Ogygia 


Trinucleus,     Asaphus,     Remopleurides. 
Amphion,  and  Triarthrus 


Calymene,  Ampyx,  nisenus,   Acidaspis, 
and  Cheirurus , 


Homalonotus  and  Lichas 

Phillipsia,  Griffithides 


GENERAL   OBSERVATIONS.  151 

The  vertical  columns  correspond  to  the  Lower  and  Upper 
Silurian,  the  Devonian,  and  the  Carboniferous.  The  left- 
hand  column  under  Lower  Silurian  corresponds  to  the  first, 
or  Primordial  period;  and  the  three  columns  under  the 
Carboniferous,  to  the  Subcarboniferous,  Carboniferous,  and 
Permian  periods  of  the  age.  The  widths  of  the  columns  are 
made  to  represent,  as  nearly  as  possible,  the  relative  lengths 
of  the  eras.  Opposite  TRILOBITES,  the  black  area  shows 
that  the  tribe  began  with  the  beginning  of  the  Paleozoic 
and  continued  nearly  to  its  end.  Next  there  are  the  names 
of  nine  genera  which  existed  only  in  the  Primordial  Period, 
each  having  then  one  or  many  species,  but  none  afterwards. 
Then  there  are  two  genera,  Olenus  and  Agnostus,  which  con- 
tinued from  the  Primordial  through  the  Lower  Silurian. 
Then,  others  confined  to  the  rest  of  the  Lower  Silurian ; 
others  that  passed  into  the  Upper  Silurian,  then  to  become 
extinct;  others  that  continued  into  the  Devonian;  and  two 
genera  confined  to  the  Carboniferous.  These  genera  included 
more  than  500  species.  Of  the  Carboniferous  genera  the 
last  species  had  been  exterminated  before  the  close  of  the 
age. 

In  a  similar  manner  the  genera  and  families  of  Brachio- 
pods  began  at  different  periods  or  epochs,  and  continued  on 
for  a  while,  to  become,  in  general,  extinct.  Many  genera 
ended  in  the  course  of  the  Paleozoic  and  at  its  close ;  only 
a  few  continued  into  later  periods. 

(4.)  Long-lived  genera. — Two  Lower  Silurian  genera  of 
Brachiopods  continue  from  the  Primordial  period,  not 
only  through  Paleozoic  and  Mesozoic  time,  but  onward  to 
the  present  age,  having  species  in  existing  seas.  They  are 
languid  and  Piscina.  It  will  be  noted  that  these  genera 
survived  through  the  long  ages  of  the  past,  not  by  the 
uninterrupted  existence  of  any  of  their  species,  but  by  the 
perpetuating  of  the  type  of  form  and  structure  character, 
izing  the  genera  in  a  succession  of  distinct  species. 


152  PALEOZOIC   TIME. 

(5.)  Unity  of  plan  in  nature. — These  long  generic  lines, 
stretching  on  with  such  uniformity  from  the  very  begin- 
nings of  life  on  the  globe,  are  proofs  of  the  unity  of  plan 
through  the  system  of  creation. 

(6.)  Permanency  of  types,  notwithstanding  the  influence  of 
external  causes. — As  this  uniformity  has  remained  in  spite  of 
the  vast  physical  changes  the  globe  has  undergone  since  life 
began,  it  is  evidence  of  the  strongest  kind  as  to  the  little 
power  which  external  causes  have  towards  producing 
changes  in  types. 

The  facts  bear  abundant  testimony  to  a  Creating  Power 
above  nature,  carrying  forward  a  preordained  plan.  More- 
over, there  is  evidence  even  in  the  Paleozoic  records — their 
coal-beds,  iron-ores,  and  the  system  of  life  in  progress  of 
expansion — that  this  plan  involved  the  future  existence  of 
a  being  that  should  have  knowledge  to  use  the  coal  and  iron, 
and  power  to  read  the  records  and  discern  in  God's  marvel- 
lous works  His  wisdom  and  beneficence. 

(7.)  General  characteristics  of  Paleozoic  life. — Both  plants 
and  animals  were  marine  through,  or  till  near  the  close  of,  the 
Silurian  age.  In  the  Devonian  age  there  were  terrestrial 
plants  and  animals,  and  a  still  greater  diversity  of  life  over 
the  land  in  the  Carboniferous.  The  characteristics  of  the 
life  of  the  Silurian  age  are  mentioned  on  page  103 ;  of  that 
of  the  Devonian,  on  page  115;  and  of  that  of  the  Carbonif- 
erous, on  page  125. 

(8.)  Special  Paleozoic  peculiarities  of  the  life. — The  follow- 
ing facts  show  in  what  respects  the  life  of  the  Paleozoic 
ages  was  peculiarly  ancient : — 

a.  Not  only  are  the  species  all  extinct,  but  almost  every 
genus.     But  15  or  16  of  the  genera  which  existed  in  the 
course  of  the  Paleozoic  have  living  species;    and  all  these 
are  Molluscan. 

b.  Among  Eadiates,  the  Polyps  were  largely  of  the  tribe 
of  Cyathophylloid  corals,  which   is   exclusively  ancient,  or 


GENERAL    OBSERVATIONS.  153 

Paleozoic,  not  a  species  having  lived  after  the  close  of  the 
Carboniferous  age.  The  Echinoderms  were  mostly  Cri- 
noids, and  these  were  in  great  profusion.  Crinoids  were 
far  less  abundant,  and  of  different  genera,  in  the  Mesozoic ; 
and  now,  very  few  exist. 

c.  Among  Mollusks,  Brachiopods  were  exceedingly  abun- 
dant :  their  fossil  shells  far  outweigh  those  of  all  other  Mol- 
lusks.   They  were  much  less  numerous  than  other  Mollusks 
in  the  Mesozoie;  and  at  the  present  time  the  group  is  nearly 
extinct.     The  Cephalopods  were  represented  very  largely 
by  Orthocerata,  but  few  species  of  which  existed  in  the  early 
Mesozoic,  and  none  afterwards. 

d.  Among  Articulates,  Trilobites  were  the  most  common 
Crustaceans, — a  group  exclusively  Paleozoic. 

e.  Among  Vertebrates,  the  Devonian  Fishes  were  either 
Ganoids  or  Selachians,  and  the  Ganoids  were  the  heterocer- 
cal  species.     Of  heteroccrcal  Ganoids,  but  few  species  lived 
in  the  first  period  of  the  Mesozoic;  and  the  whole  group  of 
Ganoids  is  now  nearly  extinct.     Of  the  Selachians,  a  large 
proportion  were  Cestracionts, — a  tribe  common  in  the  Meso- 
zoic, but  now  nearly  extinct. 

/.  Among  terrestrial  Plants,  there  were  Lepidodendra, 
Sigillarice,  Calamites  in  great  profusion,  making,  with  Coni- 
fers and  Ferns,  the  forests  and  jungles  of  the  Carboniferous 
and  later  Devonian :  no  Lepidodendron  or  Sigillaria  existed 
afterwards,  and  the  Calamites  ended  in  the  Mesozoic. 

Thus,  the  Paleozoic  or  ancient  aspect  of  the  animal  life 
was  produced  through  the  great  predominance  of  Brachio- 
pods, Crinoids,  Cyathopliylloid  Corals,  Orthocerata,  Trilobites, 
and  heterocercal  Ganoids;  and  that  of  the  plants  over  the 
land,  through  the  Lepidodendra,  Sigillaria;,  and  Calamites, 
along  with  Ferns  and  Conifers.  In  addition  to  this  should 
be  mentioned  the  absence  of  Angiosperms  and  Palms  among 
Plants ;  the  absence  of  Teliost  Fishes,  Birds,  and  Mammals, 


154  PALEOZOIC   TIME. 

among  Vertebrates ;  and  of  nearly  all  modern  tribes  of  genera 
among  Kadiates,  Mollusks,  and  Articulates. 

g.  Hesozoic  and  Modern  types  begun  in  Paleozoic  time. — The 
principal  Meso:oic  type  which  began  in  the  Paleozoic  was 
the  Eeptilian.  But  besides  Eeptiles  there  were  the  first  of 
the  Decapod  Crustaceans;  the  first  of  Oysters;  and  the  first 
of  the  great  tribe  of  Ammonites,  the  Goniatites  being  of  this 
tribe. 

The  type  of  Insects,  or  terrestrial  Articulates,  belongs 
eminently  to  modern  time;  for  it  has  now  its  fullest  dis- 
play. It  dates  from  the  existence  of  terrestrial  plants 
in  the  Devonian. 

Thus,  while  the  Paleozoic  ages  were  progressing,  and  the 
types  peculiar  to  them  were  passing  through  their  time  of 
greatest  expansion  in  numbers  and  perfection  of  structure, 
there  were  other  types  introduced  which  should  have  their 
culmination  in  a  future  age.  The  Eeptiles  and  Goniatitea 
of  the  later  Paleozoic  were  precursors  of  the  Age  of  Eep- 
tiles which  followed,  in  accordance  with  the  principle  exem- 
plified in  all  history,  that  the  characteristics  of  an  age  com- 
mence to  appear  in  the  age  preceding. 

DISTURBANCES  CLOSING  PALEOZOIC  TIME. 
1.  General  quiet  of  the  Paleozoic  Ages. — The  long  ages  of 
the  Paleozoic  passed  with  but  few  and  comparatively  small 
disturbances  of  the  strata  of  eastern  North  America.  There 
were  some  early  permanent  uplifts  in  the  Lake  Superior 
region,  and  along  the  course  of  the  Green  Mountains,  and 
some  later  in  the  district  of  Gaspe  near  St.  Lawrence  Bay ; 
there  was,  through  the  ages,  a  gradual  increase  on  the  north 
in  the  amount  of  dry  land ;  there  were,  through  parts  of  all 
the  periods,  slow  oscillations  in  progress,  varying  the  water- 
level  and  favoring  the  increasing  thickness  of  the  rocks, 
and  their  successive  variations  as  to  kind  and  extent.  But 
these  changes  were  probably  caused  by  exceedingly  slow 
movements  of  the  earth's  crust, — probably  less  than  a  foot 


APPALACHIAN    REVOLUTION.  155 

a  century.  There  may  have  been  occasional  quakings  of 
the  earth, — even  exceeding  the  heaviest  of  modern  earth- 
quakes. There  may  have  been  at  times  sudden  raisings  or 
sinkings  of  the  continental  crust.  But,  while  there  were  some 
uplifts,  as  above  mentioned,  there  is  nothing  in  the  condition 
of  the  strata  indicating  a  general  or  extensive  upturning. 

2.  The  Appalachian  the  region  of   greatest  change  of  level 
through  the  Paleozoic  Ages. — The   region  of  greatest  move- 
ment during  these  ages  was  the  Appalachian.     For  it  has 
been  shown  that  the  oscillations  which  there  took  place 
resulted  in  subsidences  of  one  or  more  thousand  feet  with 
nearly   every   period   of  the    Paleozoic.      The   oscillations 
ceased  in  the  Green  Mountain  portion  after  the  close  of  the 
Lower  Silurian  era,  but  not  until  the  subsidence  there  had 
reached  at  least  10,000  feet;  and  in  Pennsylvania  and  Vir- 
ginia they  continued  through  a  large  part  of  the  Carbonif- 
erous Age,  until  the  sinking  amounted  to  35,000  or  38,000 
feet.  But  all  this  sinking  was  probably  quiet  in  its  progress, 
as  is  proved  by  the  regularity  in  the  series  of  strata. 

The  thickness  of  the  coal-beds  indicates  that  the  coal- 
plant  marshes  were  long  undisturbed,  and  therefore  that 
long  periods  passed  without  appreciable  movement. 

3.  Approach  of  the  epoch  of  Appalachian  revolution. — The 
era  of  comparative  quiet  alluded  to  came  gradually  to  a 
close   as   the  Carboniferous   age  was  terminating,  and  an 
epoch  of  upturning,  metamorphism,  and  mountain-making 
began.     There   are   mountains   to   testify  to  this   both  in 
Europe  and  America. 

In  eastern  North  America  the  disturbances  affected  the 
Appalachian  region  and  Atlantic  border  from  Newfoundland 
to  Alabama,  and  the  Appalachian  mountains  are  a  part  of 
the  result.  The  epoch  is  hence  appropriately  styled  the 
epoch  of  the  Appalachian  revolution.  The  region  in  eastern 
America  of  the  deepest  Paleozoic  subsidence  and  of  the 
thickest  accumulation  of  Paleozoic  rocks  was  now  the 


156  CLOSE   OF   PALEOZOIC   TIME. 

region  of  the  profoundest  disturbances  and  the  greatest 
uplifts. 

4.  Effects  of  the  disturbances. — The  following  are  among 
the  effects  of  the  disturbances  along  the  Appalachian  region 
and  Atlantic  border : — 

(1.)  Strata  were  upraised  and  flexed  into  great  folds, 
many  of  the  folds  a  score  or  more  of  miles  in  span. 

(2.)  Deep  fissures  of  the  earth's  crust  were  opened,  and 
faults  innumerable  were  produced,  some  of  them  of  10,000 
to  20,000  feet. 

(3.)  Eocks  were  consolidated;  and,  over  a  large  part  of 
New  England  and  the  more  southern  Atlantic  border,  sand- 
stones and  shales  were  crystallized  into  granite,  gneiss, 
mica  and  argillaceous  schist  and  other  related  rocks,  and 
limestone  into  architectural  and  statuary  marble. 

(4.)  At  the  same  time,  the  crystallized  and  consolidated 
rocks  had  their  fractures  filled  with  mineral  material  mak- 
ing veins, — some  of  them  being  filled  with  rock  alone,  mak- 
ing veins  of  quartz,  granite,  etc.;  others  with  rock  and 
associated  metallic  minerals,  making  metallic  veins,  as  of 
lead-ore,  copper-ore,  gold;  others  were  made  containing 
gems,  as  topaz,  beryl,  and  the  like.  Diamonds,  also,  are 
among  the  results  of  the  metamorphism. 

(5.)  Bituminous  coal  was  turned  into  anthracite  in  Penn- 
sylvania and  Ehode  Island. 

(6.)  In  the  end,  the  Appalachian  mountains  were  made. 

5.  Evidence  of  the  flexures,  uplifts,  and  metamorphism. — 
The  evidence  that  the  rocks  of  the  Appalachian  region  and 
Atlantic  border  were  flexed,  uplifted,  faulted,  and  otherwise 
changed  from  their  original  condition,  is  as  follows : — 

The  Coal  measures  and  other  Paleozoic  strata,  though 
originally  spread  out  in  horizontal  beds,  are  now  in  an 
uplifted  and  flexed  or  folded  condition;  and  they  are  so 
involved  together  in  one  system  of  flexures  and  uplifts  that 


APPALACHIAN   REVOLUTION. 


157 


the  whole  must  have  been  the  result  of  one  system  of  move- 
ments.    Figures  250-253  illustrate  this. 

Fig.  250. 


Section  of  the  Coal  measures,  near  Nesquehouing,  Pa. 


Fig.  250  shows  the  condition  of  the  Anthracite  coal-beds 
of  Mauch  Chunk  in  Pennsylvania.     Some  of  the  upturned 

Fig.  251. 


Section  on  the  Schuylkill,  Pa.;  P.  Potts ville  on  the  Coal  measures;  2,  Calciferous  formation; 
3,  Trenton;  4,  Hudson  River;  5,  Oneida  and  Niagara;  7,  Lower  Helderberg;  8,  10,  11, 
Devonian ;  12,  13,  Subcarboniferous ;  14,  Carboniferous,  or  Coal  measures. 

beds,  as  is  seen,  stand  nearly  vertical.     Fig.  251  is  from 
another  locality  near  Pottsville  in  the  same  State.    The  coal 

Fig.  252. 


Section  from  the  Great  North  to  the  Little  North  Mountain  through  Bore  Springs,  Va.;  t,  t, 
position  of  thermal  springs;  n,  Calciferous  formation;  m,  Trenton;  iv,  Hudson  River; 
v,  Oneida;  vi,  Clinton  and  Lower  Helderberg ;  vn,  Oriskany  Sandstone  and  Cauda-QaUI 
Grit. 

beds  are  the  upper  ones  below  14;  the  rest  are  the  beds 
of  the  Upper  and  Lower  Silurian  (2  to  7) ;  the  Devonian  (8, 
10,  11),  and  Subcarboniferous  (12,  13).  Fig.  252  was  taken 
from  the  vicinity  of  Bore  Springs  in  Virginia,  and  includes 
Silurian  and  Devonian  beds :  it  shows  well  the  folded  cha- 


158 


CLOSE    OF   PALEOZOIC    TIME. 


racter  of  the  rocks.     Fig.  253  represents  one  of  the  great 
faults  in  southern  Virginia  (between  Walker's  Mountain  and 


Fig.  253. 


Section  of  the  Paleozoic  formations  of  the  Appalachians  iu  southern  Virginia,  between 
Walker's  Mt.  and  the  Peak  Hills  (near  Peak  Creek  Valley):  F,  fault;  a,  Lower  Silurian 
limestone;  b,  Upper  Silurian;  c,  Devonian;  d,  Subcarboniferous,  with  coal  beds. 

Peak  Hills) ;  the  break  is  at  F,  and  along  it  the  rocks  on  the 
left  were  shoved  up  along  the  sloping  fracture  until  a  Lower 
Silurian  limestone  (a)  was  on  a  level  Avith  the  Subcarbonif- 
erous formation  (d),  a  fault  of  at  least  10,000  feet.  Such 
examples  are  in  great  numbers  throughout  the  Appalachians. 
In  many  of  the  transverse  valleys  the  curves  may  be  traced 
for  scores  of  miles. 

As  shown  in  the  above  sections  (figs.  250-253),  the  folds, 
instead  of  remaining  in  regular  rounded  ridges  with  even 
synclinal  valleys  between,  such  as  the  flexing  of  the  strata 
might  make,  have  been  to  a  great  extent  worn  away,  or 
modelled  into  new  ridges  and  valleys,  by  the  action  of  waters 
during  subsequent  time ;  and  often  what  was  the  top  of  a  fold 
is  now  the  bottom  of  a  valley,  because  the  folds  would  be  most 
broken  where  most  abruptly  bent, — that  is,  along  the  axes 
of  flexure, — and  hence  would  be  most  liable  in  this  part  to  be 
cut  away  or  gorged  out  by  any  denuding  causes.  The  figures 
on  page  41  illustrate  still  further  the  condition  of  folded 
strata  before  and  after  denudation.  Some  of  the  Appala- 
chian folds  were  probably  20,000  feet  in  height  above  the 
present  level  of  the  ocean,  or  would  have  had  this  height  if 
they  had  remained  unbroken,  while  in  fact  the  loftiest  sum- 
mits now  are  less  than  7000  feet,  and  few  exceed  5000  feet. 

Over  New  England  there  are  similar  flexures.     Those  of 


APPALACHIAN    REVOLUTION.  159 

the  Ehode  Island  coal  formation  are  very  abrupt,  and  full 
of  faults,  the  coal-beds  being  much  broken  and  displaced. 
Through  eastern  Vermont,  and  in  Massachusetts  for  some 
distance  west  of  the  Connecticut  Kiver,  there  are  Devonian 
strata  in  the  same  condition;  although  the  rocks  are  in 
general  crystalline,  Devonian  fossils  have  been  found  at 
Bernardston  in  Massachusetts,  and  on  Lake  Memphremagog. 
At  the  latter  place  there  was  once  a  coral-reef  (p  105).  It 
is  inferred  from  the  facts  that  even  the  granites,  gneiss,  and 
slates  of  the  "White  Mountains,  and  the  gneiss  of  Haddam, 
Connecticut,  were  originally  Devonian  sedimentary  strata, 
and  that  all  New  England  is  made  of  folded  and  meta- 
morphosed Paleozoic  rocks. 

Similar  facts  might  be  cited  from  Nova  Scotia  on  the 
north  and  Alabama  on  the  south,  proving  that  a  region  1000 
miles  in  length  along  the  Atlantic  border,  from  Newfound- 
land to  the  Gulf  States,  participated  in  the  grand  movement. 

6.  General  truths  with  regard  to  the  results. — The  following 
are  some  of  the  general  truths  connected  with  the  uplifts 
and  metamorphism : — 

(1.)  The  courses  of  the  flexures  and  of  the  outcrops  or 
strike,  and  those  of  the  great  faults,  are  approximately 
northeast,  or  parallel  to  the  Atlantic  border.  There  is  a 
bend  eastward  in  Pennsylvania  coriesponding  with  the 
eastward  bend  of  the  southern  coast  of  New  England,  and 
then  a  change  to  the  northward  in  New  England. 

(2.)  The  folds  have  their  steepest  slope  towards  the  north- 
west, or  away  from  the  ocean.  If  fig.  41  (page  42)  represent 
one  of  the  folds,  the  left  would  be  the  ocean  side,  or  that  to 
the  southeast,  and  the  right  the  landward  side,  or  that  to 
the  northwest. 

(3.)  The  flexures  are  most  numerous  and  most  crowded 
on  that  side  of  the  Appalachian  region  which  is  towards  the 
ocean,  and  diminish  westward.  There  is  seldom,  however, 
a  gradual  dying  out  westward,  the  region  of  disturbance 


160  CLOSE   OF   PALEOZOIC    TIME. 

being  often  bounded  on  the  west  by  one  or  more  of  the 
great  fractures  and  faults,  as  in  eastern  Tennessee  and  along 
the  valley  of  the  Hudson. 

(4.)  The  wearing  away  of  the  summits  of  the  folds  when 
crowded  together  produces  a  series  of  southeast  dips,  as 
illustrated  in  figures  41,  42  (p.  42).  Such  southeast  dips, 
not  looking  as  if  they  were  ever  due  to  folds,  characterize 
the  rocks  of  much  of  Kew  England  and  the  eastern  part  of 
the  Appalachian  region. 

(5.)  The  metamorphism  of  the  strata  is  more  extensive 
and  complete  to  the  eastward  (or  towards  the  ocean)  than 
to  the  westward. 

(6.)  The  change  of  bituminous  coal  to  anthracite,  by  an 
expulsion  of  the  bitumen,  was  most  complete  where  the 
disturbances  were  greatest, — that  is,  in  the  Eastern  coal 
regions.  The  anthracite  region  of  Pennsylvania  (see  map, 
p  118)  owes  its  broken  character  partly  to  the  uplifts  and 
partly  to  denudation.  To  the  westward,  the  coal  is  first 
semibituminous,  and  then,  as  at  Pittsburg,  true  bituminous. 
In  Rhode  Island,  where  the  associated  rocks  are  partly  true 
metamorphic  or  crystalline  rocks  and  the  disturbances  aro 
very  great,  the  coal  is  an  excessively  hard  anthracite,  and 
in  some  places  is  altered  to  graphite  (an  effect  which  may 
be  produced  in  ordinary  coal  by  the  heat  of  a  furnace).  The 
bed  of  graphite  near  "Worcester  in  Massachusetts  is  sup- 
posed to  be  an  altered  coal  seam. 

7.  Conclusions. — These  facts  lead  to  the  following  conclu- 
sions : — 

(1.)  The  movement  producing  these  vast  results  was  due 
to  lateral  pressure,  the  folding  having  taken  place  just  as  it 
might  in  paper  or  cloth  under  a  lateral  or  pushing  movement. 

(2.)  The  pressure  was  exerted  at  right  angles  to  the 
courses  of  the  folds,  as  is  the  case  when  paper  is  folded  in 
the  manner  mentioned. 

(3.)  The  pressure  was  exerted  from  the  ocean  side  of  the 


APPALACHIAN   REVOLUTION.  161 

Appalachians ;  for  the  results  in  foldings  and  metamorphism 
are  most  marked  towards  the  ocean. 

(4.)  The  force  was  vast  in  amount. 

(5.)  The  force  was  slow  in  action  and  long  continued, — and 
not  abrupt  or  paroxysmal  as  when  a  wave  or  series  of 
waves  is  thrown  up  by  an  earthquake  shock  on  the  surface 
of  an  ocean.  For  the  strata  were  not  reduced  by  it  to  a 
state  of  chaos,  but  retain  their  stratification,  and  show  com- 
paratively little  confusion,  even  in  the  regions  of  greatest 
disturbance  and  alteration. 

(G.)  The  action  of  the  force  was  connected  with  the  emis- 
sion of  heat.  For  without  some  heat  above  the  ordinary 
temperature,  it  is  not  possible  to  account  for  the  consolida- 
tion and  crystallization  of  the  rocks. 

(7.)  The  history  of  the  Appalachian  Mountains  stretches 
through  all  the  geological  ages  from  the  Azoic  onward. 
Through  the  Silurian,  Devonian,  and  Carboniferous  ages, 
the  formations  were  accumulating  to  a  great  thickness, 
while  slow  oscillations  of  level  were  in  progress.  "When  the 
Carboniferous  age  was  closing,  these  oscillations,  which  had 
resulted  in  a  subsidence  of  several  miles,  began  to  culminate 
in  profounder  movements,  producing  flexures  of  the  earth's 
crust,  uplifts,  faults,  consolidation,  and  metamorphism,  and 
ending  in  the  elevation  of  the  mountains.  And  finally,  during 
these  upliftings,  moving  waters  commenced  the  work  of 
denudation, — the  chiselling  of  the  heights,  which  has  con- 
tinued to  the  present  time. 

8.  Disturbances  on  other  continents. — The  amount  of  cotem- 
poraneous  mountain-making  over  the  globe  at  this  epoch 
has  not  yet  been  clearly  made  out.  Enough  is  known  to 
render  it  probable  that  the  Ural  Mountains,,  with  their 
veins  of  gold  and  platinum,  were  made  at  the  same  time 
with  the  Appalachians,  and  that  uplifts  and  metamorphism 
also  occurred  in  other  parts  of  Europe,  and  in  Great  Bri- 
tain. Murchison  states  that  the  close  of  the  Carboniferous 


162  MESOZOIC   TIME. 

period  was  specially  marked  by  disturbances  and  uplifts ; 
that  it  was  then  "  that  the  coal  strata  and  their  antecedent 
formations  were  very  generally  broken  up,  and  thrown,  by 
grand  upheavals,  into  separate  basins,  which  were  fractured 
by  numberless  powerful  dislocations." 

The  epoch  of  the  Appalachian  revolution  was,  then,  a 
grand  epoch  for  the  world.  The  complete  extermination  of 
life  which  took  place  at  the  time  was  probably  a  consequence 
of  these  great  physical  changes  progressing  over  the  earth's 
surface.  The  Appalachian  Mountains  stand  up  as  boldly 
between  Paleozoic  and  Mesozoic  time  as  between  the  ocean 
and  the  Interior  Continental  basin. 


HE.  MESOZOIC  TIME. 

1.  Ages.— Mesozoic  or  medieval  time,  in  Geological  his- 
tory, comprises  but  one  age, — the  KEPTILIAN.    In  the  course 
of  it,  the  class  of  Reptiles  passed  its  culminations; — that  is, 
its  species  increased  in  numbers,  size,  and  diversity  of  forms, 
until  they  vastly  exceeded  in  each  of  these   respects  the 
Reptiles  of  either  eai-lier  or  later  time. 

2.  Area  of  progress  in  rock-making. — The   area  of  rock- 
making  in  North  America,  during  Mesozoic  time,  was  some- 
what different  from  what  it  was  in  Paleozoic.    Then,  nearly 
the  whole  continent,  outside  of  the  northern  Azoic,  was 
receiving  its  successive  formations;   and  the  three  great 
regions  were  the  Eastern  border,  the  Appalachian,  and  the 
Interior  Continental.     By  the  close  of  the  Paleozoic  era,  the 
Appalachian  region  and  the  Interior  east  of  the  Mississippi, 
excepting  its  southern  portion,  had  become  part  of  the  dry 
land  of  the  continent,  as  is  shown  by  the  absence  of  marine 
strata  of  later  date.     The  great  areas  of  progress  were  con- 
sequently  changed,  and   became — (1)   the  Atlantic  border, 
(2)  the  Gulf  border,  and  (3)  the  Western  Interior,  or  region 


REPTILIAN   AGE.  163 

west  of  the  Mississippi.  In  other  words,  the  continent,  from 
the  Mesozoic  onward,  until  the  close  of  the  Tertiary  period 
in  the  Cenozoic,  was  receiving  its  new  marine  formations 
only  along  its  borders  and  over  the  part  of  the  Interior 
region  which  covers  the  present  site  of  the  slopes  of  the 
Rocky  Mountains. 

These  three  regions  are  continuous  with  one  another,  the 
Atlantic  connecting  with  the  Gulf  border  region  on  the 
south,  and  the  Gulf  border  region  passing  northwestward 
into  the  "Western  Interior  or  Eocky  Mountain  region. 

In  Europe  no  analogous  change  can  be  distinguished;  for 
the  continent  was,  from  the  first,  an  archipelago;  and  it 
continued  to  bear  this  geographical  character,  though  with 
an  increasing  prevalence  of  dry  land,  until  the  Cenozoic  era 
had  half  passed.  "Western  England  then  stood  as  three  or  four 
islands  above  the  sea  (the  area  marked  as  covered  by  Paleo- 
zoic rocks  on  the  map,  p.  120),  and  the  area  of  future  rock- 
making  was  mainly  confined  to  the  intervals  between  these 
islands  and  to  the  submerged  area  on  the  east  and  southeast; 
and  it  is  probable  that  this  area  and  a  portion  of  northeast- 
ern France  were  part  of  a  large  German-Ocean  basin. 

REPTILIAN  AGE. 

Periods. — The  Reptilian  Age  includes  three  periods : — 

1.  TRIASSIC  : — named  from  the  Latin  tria,  three,  in  allusion 
to  the  fact  that  the  rocks  of  the  period  in  Germany  consist 
of  three  separate  groups  of  strata.     This  is  a  local  subdivi- 
sion, not  characterizing  the  rocks  in  Britain  or  in  most 
other  parts  of  Europe. 

2.  JURASSIC  : — named  from  the  Jura  Mountains,  situated 
on   the   eastern   border  of   France,   between   France   and 
Switzerland,  where  rocks  of  the  period  occur. 

3.  CRETACEOUS  : — named  from  the  Latin  creta,  chalk,  the 
chalk  beds  of  Britain  and  Europe  being  included  in  the 
Cretaceous  formation. 

15 


164  MESOZOIC   TIME — REPTILIAN    AGE. 

1.  TRIASSIC  AND  JURASSIC  PERIODS. 
1.  Eocks:  kinds  and  distribution. 

The  American  rocks  of  the  Triassic  period  have  not  yet 
been  separated  from  those  of  the  Jurassic,  except  in  a  few 
points  west  of  the  Mississippi. 

In  the  Atlantic  border  region,  these  Mesozoic  rocks  occupy 
narrow  ranges  of  country  parallel  with  the  Appalachian 
chain,  following  its  varying  courses.  One  of  these  ranges 
occupies  the  valley  of  the  Connecticut  between  northern 
Massachusetts  and  New  Haven  on  Long  Island  Sound, 
and  runs  parallel  with  the  Green  Mountains :  it  has  a 
length  of  about  110  miles.  Another — the  longest  of  Miem 
— commences  at  the  north  extremity  of  the  Palisades,  on 
the  west  bank  of  the  Hudson  Eiver,  and  stretches  south- 
westward  through  New  Jersey,  Pennsylvania  (here  bending 
much  to  the  westward,  like  the  Appalachians  of  the  State, 
as  shown  in  the  map  on  page  118),  and  reaching  far  into  the 
State  of  Virginia.  Another  stretches — almost  in  the  line  of 
the  last — through  North  Carolina.  There  is  another  along 
western  Nova  Scotia.  These,  and  some  other  smaller  areas, 
are  indicated  on  the  map  on  p.  69  by  an  oblique  lining  in 
which  the  lines  run  from  the  right  above  to  the  left  below. 

The  rocks  are  mainly  sandstones  and  conglomerates,  but 
include  some  considerable  beds  of  shale,  and  in  some  places 
a  bed  of  impure  limestone.  The  sandstones  are  generally 
red  or  brownish-red.  The  freestone  of  Portland,  near  Middle- 
town  in  Connecticut,  and  of  Newark  in  New  Jersey,  are 
from  the  formation.  The  pebbles  and  sand  of  the  beds  were 
derived  from  the  granites,  gneiss,  schists,  etc.  that  were 
crystallized  in  the  epoch  of  the  Appalachian  revolution; 
and  in  some  of  the  coarser  kinds  large  stones  of  granite  and 
mica  schist  may  be  taken  from  the  layers.  The  strata 
overlie  directly,  but  unconformably,  these  metamorphio 
rocks.  Near  Eichmond  in  Virginia  and  in  North  Carolina 


TRIASSIC   AND   JURASSIC   PERIODS.  165 

there  are  valuable  coal-beds  in  this  formation.  The  coal  is 
bituminous. 

The  several  ranges  of  this  sandstone  formation  are 
remarkable  for  the  great  number  of  trap  ridges  and  trap 
dikes  intersecting  them  (p.  30).  Mount  Holyoke  in  Massa- 
chusetts, East  and  West  Kocks  near  New  Haven  in  Connec- 
ticut, and  the  Palisades  on  the  Hudson,  are  a  few  examples 
of  these  trap  ridges.  Trap  is  an  igneous  rock,  one  that  was 
ejected  in  a  melted  state  from  a  deep-seated  source  of  fire, 
through  fissures  made  by  fracturing  the  earth's  crust.  The 
dikes  and  ridges  are  exceedingly  numerous,  and  have  the 
same  general  course  with  the  sandstone  ranges.  They  are 
so  associated  with  the  sandstone  formation  that  there 
appears  to  be  some  connection  in  origin  between  the  water- 
made  and  the  fire-made  rocks.  The  proofs  that  the  trap 
came  up  through  the  fissures  in  a  melted  state  are  abundant; 
for  the  wall-rock  of  the  fissures  is  often  baked  so  as  to 
be  very  hard,  and  is  sometimes  filled  with  crystallizations, 
as  of  epidote  or  tourmaline,  evidently  due  to  the  heat. 

West  of  the  Mississippi — that  is,  in  the  Western  Interior 
region — there  is  a  sandstone  formation  containing  much 
gypsum  (and  hence  called  the  Gypsiferous  formation),  which 
is  Darren  of  fossils,  except  an  occasional  fragment  or  trunk 
of  fossil  wood  and  some  Keptilian  remains.  It  probably 
spreads  widely  over  the  Eocky  Mountain  region  beneath 
the  later  beds.  It  comes  out  to  view  on  the  western  borders 
of  Kansas,  and  also  in  the  Colorado  region  beyond  the  sum- 
mit of  the  Eocky  Mountains.  Owing  to  the  absence  of 
marine  fossils,  it  has  not  been  determined  whether  the 
formation  is  Triassic,  lower  Jurassic,  or  both  united. 

In  the  vicinity  of  the  Black  Hills  in  the  region  of  the 
upper  Missouri,  there  are  some  beds  of  impure  limestone 
containing  marine  fossils  which  are  true  Jurassic.  (Meek 
and  Hayden).  These  beds  overlie  the  gypsiferous  forma- 
tion just  mentioned. 


166  MESOZOIC   TIME — REPTILIAN   AGE. 

In  Europe  the  Triassic  rocks  of  eastern  France  and  Ger- 
many, east  and  west  of  the  Ehine,  consist  of  a  Shell  lime- 
stone (called  in  German  Muschelkalk)  between  an  underlying 
thick  reddish  sandstone  (Bunter  Sandstein)  and  overlying 
strata  of  reddish  and  mottled  marlites  and  sandstone  (Keu- 
per  of  the  Germans).  In  England  (see  No.  6  on  map,  p. 
120),  the  rock  is  a  reddish  sandstone  and  marlite;  it  is 
mostly  confined  to  a  region  running  north-northwest  just 
east  of  the  Paleozoic  areas  mentioned  on  page  1G3,  and  to 
an  extension  of  this  region  westward  to  Liverpool  bay  (or 
over  the  interval  between  the  two  main  areas)  and  up  the 
west  coast. 

This  formation,  in  Europe,  contains  in  many  places  beds 
of  salt,  and  is  hence  often  called  the  Saliferous  group.  At 
Northwich  in  Cheshire,  in  England,  there  are  two  beds  of 
rock-salt,  90  to  100  feet  thick;  and  in  Europe  there  are 
similar  beds  at  Tie  and  Dieuze  in  France,  and  at  Wurtem- 
berg  in  Germany. 

The  Jurassic  rocks  of  Britain  and  Europe  are  divided 
into  three  principal  groups  : — 

1.  The  Liassic  (No.  7  a  on  map  of  England,  p.  120),  con- 
sisting of  grayish  compact  limestone  strata,  called  Lias. 

2.  The  Oolitic  (No.  7  b  on  map,  p.  120),  consisting  mostly 
of  whitish  and  grayish  limestones,  part  of  them  oolitic  (p. 
25).      One  stratum,  near  the  middle  of  the  series,  is  a  coral- 
reef  limestone,  much  like  the  reef-rock  of  existing  coral 
seas,  though  wholly  different  in  species  of  coral.     Near  the 
top  of  the  series  there  are  some  local  beds  of  fresh-water  or 
terrestrial  origin,  in  what  is  called  the  Purbeck  group,  and 
one  on  the  island  of  Portland  is  named,  significantly,  the 
Portland  dirt-bed.     The  Solenhofen  lithographic  limestone  is 
a  very  fine-grained  rock  (thereby  fit  for  lithography),  of 
the  age  of  the  Middle  Oolite,  occurring  in  Pappenheim  in 
Bavaria. 

3.  The  Wealden  (No.  8  on  the  map  of  England)  :  a  series 


TRIASSIC   AND   JURASSIC   PERIODS. 


167 


&f  beds  of  estuary  and  fresh-water* origin,  mostly  clay  and 
sand,  but  partly  of  limestone.  They  occur  in  southeastern 
England.  They  are  named  Wealden  from  the  region  where 
first  studied,  called  the  Weald,  covering  parts  of  Kent,  Surrey, 
and  Sussex. 

2.  Life. 
1.  Plants. 

The  vegetation  of  the  Triassic  and  Jurassic  periods 
included  numerous  kinds  of  Ferns,  both  large  and  small, 
Calamites,  and  Conifers,  and  so  far  resembled  that  of  the 
Carboniferous  age.  But  there  were  no  forests  or  jungles 
of  Lcpidodendra  and  Sigillarise.  Instead  of  these  Carbon- 
iferous types,  a  new  group  of  trees  and  shrubs  existed, — 
that  of  the  Cycads.  This  group  was  eminently  character- 
istic of  the  Mesozoic  world :  it  has  now  but  few  living 
species,  and  among  the  genera,  Cycas  and  Zamia  are  those 
whose  names  are  best  known. 
The  plants  have  the  aspect 
of  palms;  and  there  was, 
therefore,  in  the  Mesozoic 
forests  a  mingling  of  palm- 
like  foliage  with  that  of  Coni- 
fers (spruces,  cypress,  and 
the  like).  But  the  Cycads  are 
not  true  Palms.  They  are 
Gymnosperms,  like  the  Coni- 
fers both  in  the  structure  of 
the  wood  and  in  the  fruit. 
The  resemblance  to  Palms  is 
mainly  in  the  cluster  of  great 
leaves  at  the  summit,  and  in  Rg.  254,  Leaf  of  a  living  zamia  (x-A);  255, 

the     appearance    Of    the     OX-       Stamp    of  the  Cycad    Mantellia  (Cycadeoi- 
_  .        dea)  megalophylla  (X  &)• 

terior  of  the  trunk.    Fig.  254 

represents  the  leaf  of  a  modern  species  reduced  to  one- 
twentieth  the  actual  length;  and  fig.  255  the  trunk  of 


Figs.  254,  255. 


168 


MESOZOIC    TIME REPTILIAN    AGE. 


a  fossil  species  from  the  Portland  dirt-bed,  where  they 
are  common.  The  trunks  of  some  Cycads  have  a  height 
of  15  or  20  feet.  Although  the  form  of  the  leaf  is  palm- 
like,  the  leaflets  do  not  split  lengthwise  with  facility,  like 
those  of  Palms.  In  one  important  respect  these  Cycads 
resemble  the  Ferns, — that  is,  in  the  unfolding  of  the  young 
leaf, — the  leaf  being  at  first  rolled  up  into  a  coil,  and  gra- 

Figs.  256-260. 


Fig.  256,  Podozamites    lanceolatus;   257,  Pterophyllum    graminioides ;  258,  ClathropterU 
rectiusculus ;  259,  Pecopteris  Stuttgartensia ;  260,  Cyclopteris  linnseifolia. 

dually  unrolling  as  it  expands.  The  Cycads  thus  combine 
peculiarities  of  three  orders  of  plants, — Ferns,  Palms,  and 
Conifers, — and  are  examples,  therefore,  of  what  are  called 
comprehensive  types. 


TRIASSIC   AND   JURASSIC   PERIODS.  169 

Fossil  plants  are  common  in  the  coal  regions  of  Kiehmond, 
Virginia,  and  in  North  Carolina,  and  occur  also  in  other 
localities.  The  following  figures  represent  some  of  the  spe- 
cies. Figs.  256,  257  are  parts  of  the  leaves  of  two  species 
of  Cycads,  from  North  Carolina.  Figs.  258  to  260  repre- 
sent a  few  of  the  ferns :  fig.  258,  a  Clathropteris,  from  East 
Hampton,  Mass. ;  fig.  259,  a  Pecopteris,  from  Richmond, 
Ya.,  and  the  Trias  of  Europe ;  fig.  260,  a  Cydopteris,  from 
Richmond,  Va.  Large  cones  of  firs  have  also  been  found. 
Several  of  the  American  plants  are  identical  in  species  with 
those  of  the  European  Triassic,  and  a  few  nearer  to  Jurassic 
forms. 

2.  Animals. 
A.  AMERICAN. 

The  American  beds  of  the  Atlantic  border  region  are 
remarkable  for  the  absence  of  true  marine  life :  all  the  species 
appear  to  be  either  those  of  brackish  water,  or  of  fresh 
water  or  the  land. 

1.  Radiates  and  Hollusks. — Radiates  are  unknown.    There 
are  very  few  Mollushs  of  any  kind,  and  these  are  Conchifers. 

2.  Articulates. — The   shells  of   Ostracoid    Crustaceans  are 
common  in  Pennsylvania,  Virginia,  and  North  Carolina, 
but  have  not  yet  Jbeen  found  in  New  England.     Fig.  261 
represents  one  of  the  little  shells  of  these  bivalve 
species,  called  an  Esther ia.    It  was  long  supposed  to    Fig.  261. 
be   Molluscan.      The  Estherice  are   brackish-water 
species. 

A  few  remains  of  Insects  have  been  found,  and, 
what  is  more  remarkable,  the  tracks  of  several 
species.  These  tracks  were  left  on  the  soft  mud  probably 
by  the  larves  of  the  Insects,  for  certain  kinds  pass  their 
larval  state  in  the  water.  Fig.  262  represents  one  of  these 
larves  found  in  shale  at  Turner's  Falls  in  Massachusetts; 
it  resembles,  according  to  Dr.  Le  Conte,  the  larve  of  a 


170 


MESOZOIC   TIME — REPTILIAN   AGE. 


Figs.  262-264. 


S 


modern  Ephemera.  Figs.  263,  264  are  the  tracks  of  Insects. 
Prof.  Hitchcock  has  named  nearly  30  species  of  tracks  of 
Insects  and  Crustaceans. 

Vertebrates. — There  are  evidences  of  the  existence  of 
Fishes,  Eeptiles,  Birds,  and 
Mammals.  The  last  two  types 
here  make  their  first  appear- 
ance, and  thus  the  sub-king- 
dom of  Vertebrates  is  finally 
represented  in  all  its  classes. 

The  Fishes  found  in  the 
American  rocks  are  all  Ga- 
noids, although  Selachian  re- 
mains are  common  in  Europe. 
Fig.  265  represents  one  of  the  ^^^^^^^  202,  Paiephemera  m« 
species,  reduced  one-half.  «™  <x  i) ;  263, 2&t,  Tracks  of  insect.. 

Fig.  265. 


A 

(\ 

r\ 


r 


Kg.  265,  GANOID,  Catopterns  gracilis  (X  M);  a,  Scale  of  same,  natural  riza. 

The  Reptiles  of  the  era  are  known  to  us  partly  from  their 
fossil  bones  and  partly  from  their  footprints.  The  foot- 
prints indicate  a  wonderful  variety  as  to  form  and  size. 
Bones  have  been  found  especially  in  Pennsylvania,  North 
Carolina,  and  Nova  Scotia.  Fig.  266  represents  a  tooth, 
half  the  natural  size,  of  a  Nova  Scotia  species  (Bathygnathus 
borealis  of  Leidy);  and  fig.  267,  a  tooth  of  another,  from 
North  Carolina,  Palxosaurus  Carolinensis  Emmons.  Several 


TRIASSIC   AND   JURASSIC   PERIODS. 


171 


Kinds  occur  at  Phcenixville,  Pa.,  where  there  is  literally  a 
bone-bed. 

Figs.  268-270  represent  the  tracks  of  three  species  of 
Eeptiles  from  the  Connecticut  valley  beds;    268-270  aro 

Figs.  266-270. 


REPTILES.— Fig.  266,  Bathygnathus  borealis  (X  ^);  267,  PalaeoBanras  Carolinensis;  267  a, 
section  of  same;  268,  268  a,  fore  and  hind  feet  of  Anisopus  Deweyanus  (X  H);  269,  269  a, 
id.  of  A.  eracilis  (X  3);  270,  270  a,  id.  of  Otozoum  Moodii  (X  A). 

the  impressions  made  by  the  fore-foot  in  each,  and  268  a, 
269  a,  270  a,  of  the  hind-foot.  Fig.  270  is  reduced  to  one- 
eighteenth  the  natural  size,  the  actual  length  of  the  track 
being  20  inches.  The  animal  is  called  Otozoum  Moodii  by 
Hitchcock :  it  appears  to  have  walked  like  a  biped,  bringing 
its  fore-feet  to  the  ground  only  occasionally,  impressions  of 
these  feet  being  seldom  found.  The  animal  had  a  stride  of 
3  feet,  and  must  have  been  of  formidable  dimensions.  One 
slab,  30  feet  long,  in  the  collection  of  Amherst  College 
(Massachusetts)  contains  11  tracks  of  this  huge  animal. 
Some  of  the  Eeptiles  made  three-toed  tracks,  closely  like 


172 


MESOZOIC   TIME — REPTILIAN   AGE. 


those  of  birds;  and  this  fact  has  led  some  to  question  whe- 
ther all  may  not  be  Reptilian. 

The  tracks  regarded  as  those  of  birds  are  also  very  nume- 
rous. The  largest  of  them  is  nearly  2  feet  long  (fig.  271), 
far  exceeding  that  of  an  Ostrich,  and  even  surpassing  that 
which  the  giant  Moa  of  New  Zealand  might  have  made  (p. 

Figs.  271, 272. 


Kg.  2T1,  Track 


gigantemn(X%);  272,  Slab  of  sandstone  with  tracks  of 
Birds  and  Reptiles  (X  &). 


241).  Fig.  272  represents,  on  a  small  scale,  a  slab  from  the 
Connecticut  River  sandstone  covered  with  tracks  of  birds 
and  reptiles,  as  figured  by  Hitchcock.  The  two  tracks 
lettered  a  are  added,  of  larger  proportional  size  than  the 
others,  to  show  more  distinctly  the  form. 

The  only  relic  of  a  Mammal  yet  discovered  in  the  Ameri- 
can rocks  is  a  jawbone  (fig.  273).  It  is  from  North  Caro- 
lina, and  is  named  Dromatherium  sylvestre  by  Emmons.  It 


TEIASSIC   AND   JURASSIC   PERIODS. 


173 


Fig.  273. 


belongs  to  the  order  of  Marsupials,  the  same  which  con- 
tains the  modern  Opossum. 

The  'facts  prove  that  the  land-population  of  Mesozoic 
America  included  Insects, 
Reptiles,  Birds,  and  Marsu- 
pial Mammals,  and  that  the 
forests  that  covered  the  hills 
were  mainly  composed  of 
Conifers  and  Cycads. 

B.  FOREIGN. 

The  European  and  British  rocks  of  these  periods,  espe- 
cially of  the  Jurassic,  abound  in  marine  fossils,  and  afford  a 

Figs.  274-277. 


Jawbone  of  Dromatherium  sylvestre. 


c=» 

RADIATES.— Fig.  274,  the  Coral,  Prionastrsea  oblonga;  275,  the  Crinoid,  Encrinus  liliiformis ; 
276,  Cidaris  Blumeubachii ;  277,  Spine  of  same. 

knowledge  of  the  Mesozoic  life  of  the  ocean  which  we  fail 
to  get  from  the  American  records.  The  remains  of  terres- 
trial life  are  also  of  great  interest,  and,  like  the  American, 


174 


MESOZOIC   TIME — REPTILIAN   AGE. 


they  attest  the  existence  of  Birds  and  Mammals  in  the  course 
of  the  era. 

1.  Radiates. — Polyp-corals  are  common  in  some  Jurassic 
strata :  they  are  related  to  the  modern  tribe  of  corals,  and 
not  to  the  ancient :  none  of  the  Paleozoic  types  existed. 
Fig.  274  is  one  of  the  oolitic  species.  Crinoids  are  of  many 
kinds,  yet  their  number,  as  compared  with  other  fossils,  is 
far  less  than  in  the  preceding  ages ;  and  they  are  accompa- 
nied by  various  new  forms  of  Star-fishes  and  Echini  (p.  57). 
Fig.  275  represents  one  of  the  Triassic  Crinoids,  the  Lily- 
Encrinite,  or  Encrinus  liliiformis;  fig.  276,  an  Echinus,  from 

Figs.  25-8-281. 


Kg.  278,  Spirifer  Walcotti;  279,  Gryphaa  arcnata;  280,  Trigonia  clavellata; 
281,  Vivipara  (Palndina)  Fluviorum. 

the  Oolite,  stripped  of  its  spines,  and  fig.  277,  one  of  the 
spines  separate. 

2.  Mollusks. — Brachiopods  are  few  compared  with  the 
Paleozoic.  The  last  species  of  the  Paleozoic  families  of  the 
Spirifers  and  Leptcenas  lived  in  the  earlier  part  of  the  Juras- 
sic period.  Fig.  278  represents  one  of  these  last  of  the  Spiri- 


TEIASSIC   AND   JURASSIC   PERIODS.  175 

fer  group.  Conchifers  and  Gasteropods  abound  in  species, 
and  under  various  new,  and  many  of  them  modern,  genera. 
The  genus  Gryphcea  (fig-  279  representing  a  Liassic  species) 
is  common  in  the  Lias  and  later  Mesozoic  rocks:  it  is  an 
oyster  with  the  beak  incurved.  Trigonia  (fig.  280)  is  a  cha- 
racteristic genus  of  the  Mesozoic.  The  name  alludes  to  the 
triangular  form  of  the  shell :  the  species  figured  is  from  the 
Oolite.  Fig.  281  represents  a  fresh-water  snail-shell,  a  very 
abundant  fossil  in  fresh-water  limestone  of  the  Wealden, 
closely  resembling  many  modern  species. 

But  the  most  remarkable  and  characteristic  of  all  Mesozoic 
Mollusks  were  the  Cephalopoda.  This  order  passed  its  maxi- 
mum as  to  number  and  size  in  the  Mesozoic,  and  hundreds 
of  species  existed.  The  last  of  the  Paleozoic  type  of  Ortho- 

Figs.  282,  283. 


......  v   V    \| 

MOLLUSKS.— Fig.  282,  Ammonites  Hnmphreysianus ;  283,  A.  Jason. 

cerata  and  Goniatites  lived  in  the  Triassic  Period.  In  the 
same  period  began  the  genus  Ammonites,  the  most  common 
of  the  Mesozoic  genera,  and  in  the  earliest  Jurassic  tho 
family  of  Belemnites,  another  peculiarly  Mesozoic  type. 


16 


176  MESOZOIC   TIME — REPTILIAN   AGE. 

The  Ammonites  had  external  shells  like  the  Nautili  (p.  55). 
Two  Oolitic  species  are  represented  in  figs.  282,  283.  One 
of  them  (fig.  283)  has  the  side  of  the  aperture  very  much 
prolonged;  but  the  margin  of  the  shell,  whether  prolonged 
or  not,  is  seldom  well  preserved.  The  partitions  (or  septa) 
within  the  shells  of  Ammonites  are  bent  back  in  many  folds 
(and  much  plaited  within  each  fold)  at  their  junction  with 
the  shell,  so  as  to  make  deep  plaited  pockets.  The  front 
view  of  the  outer  plate,  with  the  entrances  to  its  side- 
pockets,  are  seen  in  fig.  284.  The  fleshy  mantle  of 
the  animal  descended  into  these  pockets,  and  thus  the 
animal  was  aided  in  holding  firmly  to  its 
shell.  The  siphuncle  in  the  Ammonites  is  Fis- 284- 
dorsal.  The  Paleozoic  Goniatites  were  of  the 
Ammonite  family,  but  the  pockets  were  much 
more  simple,  the  flexures  of  the  margins  of 
the  partitions  being  without  plications. 

The  fossil  Belemnite  is  the  internal  bone  of 
a  kind  of  Cephalopod,  analogous  to  the  pen 
or  internal  bone  (or  osselet)  of  a  Sepia,  or  Cut- 
tle-Jish  (see  fig.  289).  It  is  a  thick,  heavy  fos- 
sil, of  the  forms  in  figs.  285,  286,  having  a 
conical  cavity  at  the  upper  end.  The  fossils 
are  more  or  less  broken  at  this  extremity;  Aininoilite- tornatus. 
when  entire,  the  margin  of  the  aperture  is 
elongated  into  a  thin  edge,  and  sometimes,  on  one  side,  into 
a  thin  plate  of  the  form  in  fig.  287.  The  animal  had  an  ink- 
bag  like  the  modern  Sepia;  and  ink  from  these  ancient 
Cephalopods  has  been  used  in  sketching  their  fossil  remains. 
Fig.  288  represents  one  of  the  ink-bags  of  the  Jurassic 
Cephalopods.  Fig.  289  is  another  related  Cephalopod,  show- 
ing something  of  the  form  of  the  animal,  and  also  the  ink- 
bag  in  place. 

3.  Articulates. — The  Articulates  included  various  shrimps, 
or  craw-fishes  (fig.  290,  a  Triassic  species),  Crabs,  and  Te- 


TRIASSIC   AND   JURASSIC   PERIODS. 


177 


tradecapod  (or  14-footed)  Crustaceans  (fig.  291,  represent- 
ing a  species  something  like  the  modern  Sow-bug},  but  no 


Figs.  285-289. 


MOLLCSKS.— Fig.  285,  Belemnitcs  pistilliformia ;  286,  B.  paxillosus ;  286  a,  Outline  of  section 
of  same,  near  extremity;  287,  View,  reduced,  of  the  complete  osselet  of  a  Belemnite;  288, 
Fossil  Ink-bags  of  a  Cephalopod;  289,  Acanthoteuthis  antiquus. 

Trilobites;  also  the  first  known  of  true  Spiders  (fig.  292), 
and  species  of  many  of  the  orders  of  Insects.  Fig.  293  is  a 
Libellula,  or  Dragon-fly,  of  the  Jurassic  period,  from  Solen 


178 


MESOZOIC   TIME — REPTILIAN    AGE. 


hofen;  and  fig.  294,  the  wing-case  of  a  beetle,  from  the 
Stonesfield  Oolite. 

Figs.  290-294. 


AKTICUIATZS.— Fig.  290,  Pemphix  Sueurii;  291,  Archseoniscus  Brodiet;  292,  Palpipes  priscui; 
293,  Libellula ;  294,  Wing-case  of  a  Buprestis. 

3.  Vertebrates. — The  Fishes  were  all  either  Ganoids  or  Sela- 
chians. In  the  Triassic  beds  occurred  the  last  species  of  the 
heterocercal  Ganoids,  and  the  first  of  the  homocercal,  along 
with  some,  like  fig.  265,  p.  170,  of  intermediate  character, — 
that  is,  having  the  tail-fin  vertebrated  through  half  its 
length.  Fig.  295  represents  one  of  the  homocercal  Ganoids 
of  the  Lias.  Among  the  Sharks  (or  Selachians)  the  Cestra- 
ciont  tribe,  the  most  ancient,  characterized  by  a  pavement 
of  grinding  teeth  (p.  52),  still  continued,  and  was  very 
numerously  represented.  There  were  also  in  the  Jurassic 
beds  the  first  of  the  sharp-edged  Shark-teeth,  or  those  of 
the  tribe  of  Sharks  that  inhabits  modern  waters. 

Reptiles  were  the  dominant  race  in  the  Reptilian  world, 
and  among  them  were  Amphibians,  the  division  most  com- 
mon in  the  Carboniferous  age,  and  also  great  numbers  of 


TRIASSIC   AND   JURASSIC   PERIODS. 


179 


true  Reptiles.     They  included  species  for  each  of  the  ele- 
ments,— the  water,  the  earth,  and  the  air. 
In  the  Triassic  the  Amphibian  division   (p.  50)    appears 

Fig.  295. 


VERTEBRATE.— Fig.  295,  Restored  figure  of  ^chmodus  (Tetragonolepis)  (X%);  296  o,  Scale* 
of  same. 

to  have  reached  its  maximum.     One  of  the  frog-like  Laby- 
rinthodonts  had  a  skull  of  the  form  shown  in  fig.  296,  whose 

Figs.  296-298. 


VERTEBRATES.— Fig.  296,  Skull  of  Mastodonsaurus  Jaegeri  (X  A) !  297.  Tooth  of  same  (X  K): 
298,  Footprints  of  Cheriotherium  (X  A)- 

length  was  3  to  4  feet ;  its  mouth  was  set  around  with  teeth 
3  inches  long  (fig.  297),  and  the  body-  was  covered  with 
scales.  The  specimen  figured  was  found  in  Saxony.  It  is 

16* 


180 


MESOZOIC   TIME — REPTILIAN    AGE. 


probable  that  some  of  the  American  Reptilian  species 
whose  tracks  are  so  common  in  the  Connecticut  valley 
were  of  this  type.  Fig.  298  is  a  reduced  view  of  hand- 
like  tracks,  from  the  same  locality  as  the  above,  sup- 
posed to  have  been  made  by  an  animal  of  the  same  species. 
The  frogs  of  the  present  day  are  feeble  and  diminutive  com- 
pared with  the  Triassic  Amphibians. 

Swimming  Eeptiles,  or  Saurians, — called  Enaliosaurs 
because  of  their  living  in  the  sea  (from  the  Greek  enalios, 
marine,  and  sauros,  lizard), — probably  existed  in  the  Carbon- 
iferous age  (p.  135)  :  they  became  numerous  and  of  great  size 
in  the  Mesozoic.  They  had  paddles  like  "Whales,  and  thus 

Figs.  299-304. 


VEETEBBATES.— Fig.  299,  Ichthyosaurus  communls  (XiJo);  300,  Head  of  same  (X&);  301a. 
301  b,  View  and  section  of  vertebra  of  same  (X  %) !  302>  Tooth  of  same,  natural  size ;  003, 
Plesiosaurus  dolichodeirus  (X  A,);  304  a,  304  b,  View  and  section  of  vertebra  of  same. 

were  well  fitted  for  marine  life.     The  most  common  kinds 
were  the  Ichthyosaurs  and  Plesiosaurs. 


TRIASSIC    AND   JURASSIC   PERIODS.  181 

The  Ichthyosaurs  (fig.  299)  had  a  short  neck,  a  long  and 
large  head,  enormous  eyes,  and  thin,  fish-like,  or  doubly- 
concave,  vertebra?.  The  name  is  from  the  Greek  ichthus,  fish, 
and  saur.  Fig.  300  represents  the  head  of  a'n  Ichthyosaur, 
one-thirtieth  the  natural  length,  showing  the  large  size  of  the 
eye  and  the  great  number  of  the  teeth.  Fig.  301  b  is  one 
of  the  vertebrae,  reduced,  and  fig.  301  a,  a  transverse  section 
of  the  same,  exhibiting  the  fact  that  both  surfaces  are  deeply 
concave,  nearly  as  in  fishes;  fig.  302  is  one  of  the  teeth,  natu- 
ral size.  Some  of  the  Ichthyosaurs  were  30  feet  long. 

The  Plesiosaurs  (named  from  the  Greek  plesios,  near,  and 
saur,  because  not  quite  like  a  Saurian),  one  of  which  is 
represented  very  much  reduced  in  fig.  303,  had  a  long  snake- 
like  neck,  a  comparatively  short  body,  and  a  small  head. 
Fig.  304  a  represents  one  of  the  vertebras,  and  304  b,  a  sec- 
tion of  the  same;  it  is  doubly-concave,  but  less  so,  and  much 
thicker,  than  in  the  Ichthyosaurs.  Some  species  of  Plesio- 
saur  were  25  to  30  feet  long.  Another  related  Eeptile,  called 
a  Pliosaur,  was  30  to  40  feet  long.  Remains  of  more  than 
50  species  of  Enaliosaurs  have  been  found  in  the  Jurassic 
rocks. 

Besides  these  swimming  Saurians,  there  were  numerous 
species  of  Lacertians  (Lizards)  and  Crocodilians  10  to  50 
feet  long,  and  Dinosaurs,  the  bulkiest  and  highest  in  rank 
of  the  Saurians,  25  to  60  feet  long. 

To  the  group  of  Dinosaurs  belongs  the  Iguanodon,  of  the 
Wealden  beds,  first  made  known  by  Dr.  Mantell,  whose  body 
was  28  to  30  feet  long,  and  which  stood  high  above  the 
ground  quadruped-like,  the  femur,  or  thigh-bone,  alone 
being  nearly  3  feet  long.  Its  habits  are  supposed  to  have 
been  like  those  of  a  Hippopotamus— -the  animal  grazing 
on  the  plants  and  shrubs  of  the  marshes,  estuaries,  or 
streams  in  or  about  which  it  lived.  It  had  teeth  like  the 
modern  Iguana  (and  hence  the  name,  from  Iguana,  and  tho 
Greek  odous,  tooth),  but  it  had  proportionally  a  much  shorter 


182 


MESOZOIC    TIME REPTILIAN    AGE. 


tail.  The  Megalosaur  was  another  of  the  gigantic  Dinosaurs 
of  the  later  part  of  the  Jurassic  period;  it  was  a  terrestrial 
carnivorous  Saurian,  about  30  feet  in  length. 

The  Beptiles  adapted  for  the  air — that  is,  for  flying — are 
designated  Pterosaurs,  from  the  Greek  pteron,  a  wing,  and 
saur.  The  most  common  genus  is  called  Pterodactylus.  The 
general  form  of  a  Pterodactyl  is  shown  in  fig.  305.  The  bone 
of  one  of  the  fingers  is  greatly  elongated,  for  the  purpose  of 

Fig.  305. 


VEKTEBRATE. — Pterodactylus  crassirostris  (X  /£)• 

supporting  an  expanded  membrane,  so  as  to  make  it  serve 
(like  an  analogous  arrangement  in  bats)  for  flying.  The 
name  Pterodactyl  is  from  the  Greek  pteron,  wing,  and  dak- 
tulos,  finger.  The  Pterodactyls  were  mostly  small,  and  proba- 
bly had  the  habits  of  bats;  the  largest  had  a  spread  of  wing 
of  about  10  feet.  Unlike  birds,  they  had  a  mouth  full  of 
teeth,  and  no  feathers.  As  Bats  are  flying  Mammals,  so  the 
Pterosaurs  are  simply  flying  Eeptiles,  and  have  no  resem- 
blance to  birds  in  structure,  except  that  their  bones  are 
hollow. 


TRIASSIC   AND   JURASSIC    PERIODS. 


183 


Besides  the  kinds  of  Eeptiles  already  mentioned,  there 
were  Turtles  in  the  Jurassic  period;  but,  according  to  pre- 
sent knowledge,  the  world  contained  no  Snakes. 

Coprolites  (or  fossil  excrements)  of  both '  Eeptiles  and 
Fishes  are  common  in  the  bone-beds.  When  cut  and 
polished  they  have  a  degree  of  beauty  sufficient  to  have 
made  them  formerly  an  object  of  some  value  in  jewelry. 

Remains  of  Birds  have  been  found  in  the  quarries  of 
Solenhofen  (p.  166).  They  have  revealed  the  fact  that  some 
at  least  of  the  Mesozoic  species  (and  of  America,  beyond 
question,  as  well  as  Europe)  were  reptilian  in  some  of  their 
characters.  The  skeleton  found  shows  that  the  Birds  had 
long  reptile-like  tails  consisting  of  many  vertebrae,  and 
finger-like  claws  on  the  fore  limb  or  wing,  like  those  of  the 
Pterodactyl  and  Bat,  fitting  them  evidently  for  clinging. 
But,  while  thus  reptilian  in  some  points  of  structure,  they 
were  actually  Birds,  being  feathered  animals,  and  having 
the  expanse  of  the  wing  made,  not  by  an  expanded  mem- 
brane as  in  the  Pterodactyl,  but  by  long  quill-feathers. 

Figs.  306,  307. 


VERTEBRATES.— Fig.  306,  Amphitherium  Broderipii  (X  2) ;  307,  Phascolotherium  Bncklandi 
(X2). 

The  tail-quills  were  arranged  in  a  row  either  side  of  the 
long  tail.     The  feet  were  precisely  like  those  of  birds. 


184  MESOZOIC   TIME — REPTILIAN    AGE. 

Eemains  of  Mammals  occur  in  the  Upper  Trias  (or  base 
of  the  Lias)  of  Germany,  in  the  Lower  Oolite  deposit  at 
Stonesfield,  England,  and  in  the  Portland  "  dirt-bed"  of  the 
Upper  Oolite  (p.  166).  Nearly  20  species  have  been  made 
out,  14  of  them  from  relics  in  the  Portland  "  dirt-bed."  The 
larger  part  are  Marsupials;  a  few  are  pronounced  to  be  non- 
marsupial  Mammals  of  the  order  of  Insectivores.  Figs.  306, 
307  represent  the  jaws  of  two  species  from  Stonesfield,  mag- 
nified twice  the  natural  size. 

As  Marsupials  are  semi-oviparous  Mammals,  and  therefore 
are  intermediate  between  ordinary  Mammals  and  the  inferior 
and  oviparous  Vertebrates  (p.  50),  it  follows  that  both  the 
Birds  and  Mammals  of  the  Mesozoic  were  in  part,  at  least, 
comprehensive  or  intermediate  types,  and  partook  of  reptilian 
features  in  the  Eeptilian  age. 

3.  General  Observations. 

1.  American  Geography. — The  Mesozoic  sandstones  and 
shales  of  the  Atlantic  border  region  are  sedimentary  beds; 
consequently,  the  long  narrow  ranges  of  country  in  which 
they  were  formed  were  occupied  at  the  time  more  or  less 
completely  by  water. 

The  absence  of  true  marine  fossils  has  been  remarked 
upon  as  proving  that  this  water  was  either  brackish  or 
fresh;  and  hence  the  areas  were  estuaries  or  deep  bays 
running  far  into  the  land. 

There  was  probably  an  abundance  of  marine  life  in  the 
ocean,  if  we  may  judge  from  its  diversity  on  the  other  side 
of  the  Atlantic ;  but  the  seacoast  of  the  era  must  have  been 
outside  of  the  present  one,  so  that  any  true  marine  or  sea- 
coast  deposits  that  were  made  are  now  submerged.  The 
present  sea-border  is  shallow  for  a  distance  of  80  miles  from 
the  New  Jersey  coast,  the  depth  of  water  at  this  distance 
out  being  but  600  feet. 


TRIASSIC   AND   JURASSIC   PERIODS.  185 

As  all  the  depressions  or  valleys  occupied  by  the  estuaries 
are  parallel  with  the  Appalachians  (p.  164),  and  since  the 
era  of  the  formations  was  that  next  following  the  origin  of 
these  mountains,  the  depressions  must  have  been  made  at 
the  time  the  Appalachian  foldings  were  in  progress.  In  fact, 
they  are  some  of  the  great  valleys  or  depressions  left  in  the 
course  of  the  upliftings. 

The  level  of  the  several  sandstone  areas  above  the  ocean 
proves  that  the  land  at  the  time  was  not  far  from  its  present 
elevation,  and  therefore  that  the  Appalachians  had  probably 
nearly  their  present  he'ight. 

The  deposits  contain  foot-prints,  ripple-marks,  rain-drop 
impressions,  and  other  evidences,  on  many  of  the  layers, 
that  they  were  formed  partly  in  shallow  waters,  and  partly 
as  sand-flats,  or  emerging  marshes  and  shores,  over  which 
reptiles  and  birds  might  have  walked  or  waded.  If,  then, 
they  are  several  thousands  of  feet  thick,  there  must  have 
been  a  progressing  subsidence  of  the  valley-depressions — 
that  is,  a  sinking  must  have  been  going  on.  It  is  hence 
apparent  that  the  oscillations  of  level  that  characterized 
the  epoch  of  the  Appalachian  revolution  were  still  in  pro- 
gress. Two  effects  of  this  subsidence  occurred : — (1)  The 
sandstone  beds  were  more  or  less  faulted  and  tilted,  those 
of  the  Connecticut  valley  receiving  a  dip  to  the  eastward, 
those  of  New  Jersey  and  Pennsylvania  to  the  northwest- 
ward. (2)  In  the  sinking  of  the  valley-depression,  an 
increasing  strain  was  produced  in  the  earth's  crystalline 
crust  beneath,  which  finally  became  so  great  that  the  crust 
broke,  fissures  opened,  and  liquid  rock  came  up.  The  dikes 
and  ridges  of  trap  are  this  liquid  rock  solidified  by  cooling. 
The  existence  of  the  dikes,  and  their  parallelism  to  the 
general  course  of  the  valley-depressions,  prove — (1)  the  fact 
of  the  fractures;  (2)  their  resulting  from  the  same  cause 
which  produced  the  sinking;  and  (3)  the  fact  of  the  igneous 
ejections.  The  earth's  crust  along  the  Connecticut  valley 


186  MESOZOIC   TIME — REPTILIAN    AGE. 

was  thus  a  scene  of  igneous  operations  for  a  length  over  100 
miles,  and  through  a  vast  number  of  opened  fissures.  The 
Palisades  of  the  Hudson  date  from  the  same  period, — pro- 
bably the  middle  of  the  Jurassic  period. 

The  Western  Interior,  or  Rocky  Mountain  region,  had  been 
mostly  submerged  during  the  Carboniferous  age,  as  shown 
by  the  fact  that  limestones  were  forming  there  in  the  Coal 
Measure  period,  and  fossiliferous  sandstones  in  the  Permian. 
The  Gypsiferous  sandstone  of  the  Mesozoic  proves,  by  its 
naturc;  its  gypsum,  and  its  rare  fossils,  that,  by  some  change, 
this  great  region  had  become  mostly'an  interior  shallow  salt 
sea,  shut  off  to  a  great  extent  from  the  ocean.  Such  a  sea 
would  have  been  made  too  fresh  for  marine  life  in  the  rainy 
season,  and  probably  too  salt  for  any  life  in  the  hot  season. 
Hence,  as  in  the  Great  Salt  Lake  of  Utah,  life  would  have 
been  absent.  The  salt  waters  by  evaporation  would  have 
furnished  gypsum  to  the  beds,  as  happens  now  sometimes 
from  sea-water.  It  follows,  then,  from  the  beds  of  the 
Atlantic  border  as  well  as  those  of  the  Western  Interior, 
that  the  continent  during  the  era  of  these  Mesozoic  beds 
was  to  a  less  extent  submerged  than  in  the  greater  part 
of  the  Paleozoic  ages  and  the  following  portion  of  the 
Mesozoic.  The  fossiliferous  Jurassic  beds  mentioned  on 
page  165  show  that  before  the  Jurassic  period  had  closed, 
the  sea  had  again  free  access  over  it;  and  the  later  Cre- 
taceous formations  prove  that  in  the  Cretaceous  period 
also  this  marine  condition  prevailed. 

2.  Foreign  Geography. — The  nature  of  the  Triassic  beds 
of  Britain  and  Europe  show  that  there  were  large  shallow 
interior  seas  also  on  the  eastern  side  of  the  Atlantic.  The 
salt-deposits  in  the  beds,  the  paucity  of  fossils  in  the  most 
of  the  strata,  and  the  prevalence  of  marlites,  indicate  the 
same  conditions  as  existed  in  New  York  during  the  forma- 
tion of  the  Saliferous  beds  of  the  Upper  Silurian  (see  page 
95),  and  somewhat  similar  to  those  in  which  the  Kocky 


TRIASSIC   AND   JURASSIC   PERIODS.  187 

Mountain  Gypsiferous  formation  originated.  The  limestone 
that  intervened  along  the  Ehine,  between  the  two  forma- 
tions of  sandstone  and  marlites,  shows  an  interval  of  more 
open  sea ;  yet  the  impurity  of  the  limestone  suggests  that 
the  ocean  had  not  full  sweep  over  the  region. 

The  beds  of  the  Jurassic  period  are  almost  all  of  them 
evidence,  both  from  their  constitution  and  their  abundant 
marine  life,  that  the  free  ocean  again  had  sway  over  large 
portions  of  the  Continental  area.  Its  limits,  however, 
became  more  contracted  as  the  period  passed,  and  towards 
its  close  fresh-water  and  terrestrial  beds  were  forming  in 
some  places  that  had  earlier  in  the  period  been  under  salt 
water. 

3.  Climate. — The  Jurassic  coral  reefs  of  Britain  indicate 
that  England  then  lay  within  the  sub-tropical  oceanic  zone. 

This  zone  now  has  the  parallel  of  27°  to  28°  as,  in  general, 
its  outer  limit  (lying  mostly  between  20°  and  27°);  and,  con- 
sequently, its  Jurassic  limit,  if  including  England,  reached 
twice  as  far  towards  the  pole  as  now.  It  is  possible,  how- 
ever, that  the  line  ran  along  the  British  Channel,  and  that 
the  Gulf  Stream  of  the  era  carried  the  sub-tropical  tempera- 
ture northeastward  through  the  British  seas,  as  it  now 
does  to  Bermuda,  in  latitude  34°. 

The  following  are  other  facts  of  similar  import.  In  Arctic 
America,  species  of  shells  allied  to  those  of  Europe  and 
tropical  South  America  occur  in  latitudes  60°  to  77°  16'; 
and  one  species  of  Selemnite  and  one  of  Ammonite  are  said  to 
be  identical  with  species  occurring  in  these  two  remote  and 
now  widely  different  regions.  If  not  absolutely  identical, 
the  evidence  from  them  as  to  oceanic  temperature  is  nearly 
the  same.  Moreover,  on  Exmouth  Island,  in  77°  16'  N., 
remains  of  an  Ichthyosaur  have  been  found,  and  in  76°  22' N., 
on  Bathurst  Island,  bones  of  other  large  Jurassic  Eeptiles 
(Teleosaurs~).  It  is  probable,  therefore,  that  a  warm-tempe- 
rate oceanic  zone  covered  the  Arctic  to  the  parallel  of  78°, 
17 


188  MBSOZOIC   TIME — REPTILIAN   AGE 

if  not  beyond.     No  large  living  reptiles  exist  outside  of  the 
warm-temperate  zone. 

2.  CRETACEOUS  PERIOD. 

General  characteristics. — The  Cretaceous,  while  the  closing 
period  of  Mesozoic  time,  was  also,  in  some  respects,  a 
transition  period  between  the  Mesozoic  and  Cenozoic. 
During  its  progress,  as  is  explained  beyond,  occurred  the 
decline,  and,  at  its  close,  the  extinction,  of  a  large  number 
of  the  tribes  of  the  medieval  world,  while,  at  the  same  time, 
there  appeared  in  its  course  other  tribes  eminently  charac- 
teristic of  the  modern  world.  Among  these  modernizing 
features,  the  most  prominent  arose  from  the  introduction  of 
Palms  and  Angiosperms  among  plants,  and  Teliosts  among 
fishes. 

The  Palms  and  Angiosperms  include  nearly  all  the  fruit- 
trees  of  the  world,  and  constitute  far  the  larger  part  of 
modern  forests.  The  Conifers  and  Cycads,  wherever  they 
now  occur  near  groves  of  Angiosperms,  exhibit  the  contrast 
between  the  medieval  foliage  and  that  of  the  present  age. 
The  Teliosts  (p.  50)  embrace  nearly  all  modern  fishes 
excepting  those  of  the  order  of  Sharks,  or  Selachians. 
Their  appearance  was  as  great  a  change  for  the  waters  as 
the  new  tribes  of  plants  for  the  land.  These  tribes  of  plants 
and  fishes  were  only  begun  in  the  Cretaceous :  their  full 
exhibition  belongs  to  Cenozoic  time  and  the  Age  of  Man. 

1.  Rocks:  kinds  and  distribution. 

In  North  America,  the  Cretaceous  formation  borders  the 
continent  on  the  Atlantic  side,  eouth  of  New  York,  and 
along  the  north  and  west  sides  of  the  Gulf  of  Mexico; 
besides,  it  spreads  from  Texas,  northward,  over  the  slopes 
of  the  Eocky  Mountains,  being  now  at  a  height  in  some 
places  of  6000  to  7000  feet  above  the  sea.  Its  beds  are 
exposed  to  view  in  New  Jersey  and  in  some  portions  of  the 


CKETACEOUS    PERIOD  189 

more  southern  Atlantic  States,  though  mostly  covered  by 
the  Tertiary.  They  are  largely  displayed  through  Alabama 
and  Mississippi,  and  cover  a  great  area  west  of  the  Missis- 
sippi. (Sec  map,  p.  69). 

In  England  the  formation  occupies  a  region  just  cast  of 
the  Jurassic,  stretching  from  Dorset  on  the  British  Channel 
cast-ward,  and  also  northeastward  to  Norfolk  on  the  German 
Ocean,  and  continuing  near  the  borders  of  this  ocean,  still 
farther  north,  beyond  Flamborough  Head  :  it  is  numbered  9 
on  the  map,  p.  120.  Cretaceous  rocks  occur  also  in  northern 
and  southern  France,  and  many  other  parts  of  Europe. 

Among  the  rocks  there  arc  the  following  kinds  : — the  soft 
variety  of  limestone  called  Chalk;  hard  limestones;  ordi- 
nary hard  sandstones ;  shales  and  conglomerates  like  those 
of  other  .ages;  but,  more  common  than  these,  soft  sand- 
beds,  clay-beds,  and  shell-beds,  so  imperfectly  consolidated 
that  they  may  be  turned  up  with  a  pick. 

Many  of  the  sand-beds  or  sandstones  have  a  dark-green 
color,  and  are  called  green-sand.  The  green  color  is  owing 
to  the  presence  of  dark-green  grains  which  occur  mixed 
with  more  or  less  of  common  sand.  They  are  a  hydrous 
silicate  of  iron  and  potash.  This  green-sand  is  often  used 
for  fertilizing  land,  and  when  so  used  it  is  called  marl. 

Chalk-beds  are  the  source  of  flint.  The  flint  is  distributed 
through  the  chalk  in  layers,  these  layers  being  made  up  of 
nodules  of  flint,  or  masses  of  irregular  forms.  Although 
often  of  rounded  forms,  they  are  not  water-worn  stones  of 
foreign  origin,  but  were  formed  in  place,  like  the  hornstone 
in  the  Corniferous  limestone  of  New  York  (p.  105). 

Chalk  constitutes  a  large  proportion  of  the  Cretaceous 
formation  in  England  and  some  parts  of  Europe,  but  is  not 
known  in  the  American  Cretaceous.  The  succession  of  beds 
in  England  is  as  follows :— (1)  The  Lower  Cretaceous,  con- 
sisting largely  of  the  Green-sand  and  other  arenaceous 
beds,  called  collectively  the  Lower  Green-sand;  (2)  the 


190  MESOZOIC    TIME — REPTILIAN   AGE. 

Middle  Cretaceous,  containing  the  Upper  Green-sand  and 
some  other  beds;  (3)  the  Upper  Cretaceous,  comprising  tho 
Chalk-beds,  the  lower  part  of  which  is  without  flints. 

The  Cretaceous  beds  in  North  America  are  supposed  to 
correspond  to  the  Middle  and  Upper  of  the  European  Cre- 
taceous. They  consist  of  layers  of  Green-sand,  thick  sand- 
beds  of  other  kinds,  clays,  shell-beds,  and,  in  some  places  in 
the  States  bordering  on  the  Mexican  Gulf  (especially  in 
Texas),  limestone.  The  thickness  of  the  formation  in  New 
Jersey  is  400  to  500  feet ;  in  Alabama,  2000  feet ;  in  Texas, 
about  800,  nearly  all  of  it  compact  limestone ;  in  the  region  of 
the  Upper  Missouri,  2000  to  2500  feet. 

2.  Life. 
1.  Plants. 

The  first  of  Angiosperms  and  of  Palms,  as  already  stated, 
date  from  the  Cretaceous  period.  Leaves  of  a  few  Ameri- 
can species  of  the  former  are  represented  in  figs.  308-311 ; 
fig.  309,  from  a  species  of  Sassafras;  fig.  310,  a  Liriodendron ; 
and  fig.  311,  a  Willow ;  and  with  these  occur  leaves  of  Oak, 
Dogwood,  Beech,  Poplar,  &c. 

Besides  these  highest  of  plants,  there  were  also  Conifers, 
Ferns,  and  Sea-weeds,  as  in  former  time,  with  some  Cycads 
still.  The  microscopic  Alga?  called  Diatoms  (p.  61),  which 
make  siliceous  shells,  and  others  called  Desmids  (p.  61), 
which  consist  of  one  or  a  few  simple  green  cellules,  were 
very  abundant.  Both  occur  fossil  in  flint;  and  a  species  of. 
the  latter  is  very  similar  to  one  from  the  Devonian  horn- 
stone  figured  on  page  110  (fig.  180).  The  Diatoms  arc  believed 
to  hare  contributed  part  of  the  silica  of  which  the  flint  is 
formed. 

2.  Animals. 

1.  Protozoans. — The  simplest  of  animals,  Rlrizopods,  of  the 
group  of  Protozoans  (p.  59),  were  of  great  geological  im- 
portance in  the  Cretaceous  period;  for  the  Chalk  is  supposed 


CRETACEOUS   PERIOD.  191 

to  be  made  mostly  from  their  minute  calcareous  shells.    The 

powdered  chalk  is  often  found  to  contain  large  numbers  of 

Figs.  308-311. 


Fig.  308,  Leguminosites  Marcouanus;  309,  Sassafras  Cretaceum;  310,  Liriodendron  Meekii; 
311,  Salix  Meekii. 

these  shells,  the  great  majority  of  which  do  not  exceed  a 
pin's  head  in  size.  A  few  of  the  forms  are  represented  in 
Figs.  312-316. 


RHIZOPODS:  Fig  312,  Lituola  nautiloidea;  313,  Flabellina  mgosa;  314,  Chrysalidiiia  gradata 
315,  Cuneolina  pavonia ;  316,  Orbitoliua  Texaiia. 
17* 


192  MESOZOIC    TIME — REPTILIAN    AGE. 

figs.  312  to  316,  all  very  much  enlarged,  except  316,  which  is 
natural  size.  A  very  common  kind  resembles  fig.  99,  p. 
59,  and  is  called  a  Rotalia.  Fig.  316  represents  a  large 
disk-shaped  species,  called  an  Orbitolina,  from  Texas. 

Besides  the  above  Protozoans,  Sponges  were  also  very 
abundant,  and  their  siliceous  spicula  (p.  58)   were  another 
important  source  of  the  silica  of  the 
flints.    Fig.  317  represents  one  of  the 
Sponges  from  the  Chalk  of  Europe. 

2.  Radiates  —  Mollusks.  —  Corals 
and  Echini  were  common  among 
Eadiates.  Mollusks  abounded,  both 
of  the  Ammonite  and  Belemnite 
types,  besides  others  of  genera  not 
peculiar  to  the  Mesozoie.  Many  of 
the  genera  are  identical  with  those 

i    .  j  Siphonia  lobata. 

represented  in  modern  seas. 

Figs.  318-321. 


MOLLUSKS  :  Fig.  318,  Exogyra  costata ;  319,  Inoceramus  problematicus ;  320,  Gryplicea  vesici* 
laris;  321,  G.  Pitcheri. 


CRETACEOUS  PERIOD. 

Figs.  322-328. 


193 


MoixusKS:  Fig.  322,  Fasciolaria  buccinoides ;  323,  Fusus  Newberryi;  324,  Ammonites  Pla- 
centa;  324 a,  id.,  in  profile,  reduced;  325,  Scaphitea  larvajformis ;  326,  Turrilites  catenates; 
327.  Baculitesovatus;  328  Belemnitella  mucronata. 


194  MESOZOIC   TIME — REPTILIAN    AGE. 

Pigs.  318-321  are  of  some  of  the  most  characteristic  Con- 
chifers  from  the  American  Cretaceous;  fig.  318,  an  Exogyra; 
fig.  319,  an  Inoceramus;  figs.  320, 321,  Gryphceas : — genera  that 
are  now  extinct.  Figs.  322, 323  represent  shells  of  Gastero- 
poda, and  324  to  328,  Cephalopods, — all  American  except 
3^6;  fig.  324,  an  upper  front  view  of  an  Ammonite,  showing  the 
pockets  along  the  sides  of  one  of  the  partitions ;  fig.  324  a, 
a  reduced  view  of  the  same  Ammonite  in  profile ;  figs.  325 
to  327,  three  species  of  the  Ammonite  family,  but  not  of  the 
genus  Ammonites, — one,  fig.  325,  being  called  a  Scaphites 
(from  the  Latin  scapha,  a  skiff),  an  Ammonite  with  the  shell 
looking  as  if  partly  uncoiled,  and  thus  made  somewhat  to 
resemble  a  boat ;  fig.  326,  a  Turrilites,  or  turreted  Ammonite, 
an  anomaly  in  the  family,  as  the  species  are  almost  all 
coiled  in  a  flat  plane;  fig.  327,  a  Baculitcs,  or  straight  Ammon- 
ite, so  named  from  the  Latin  baculum,  a  walking-stick. 
Fig.  328  represents  a  very  common  New  Jersey  species  of 
Belemnites.  Some  of  the  Ammonites  of  the  Cretaceous 
period  are  3  to  4  feet  in  diameter. 

3.  Vertebrates. — Among  Vertebrates  appeared  the  first  of 

Fig.  329. 


Osmeroides  Lewesien&is  (X  %)• 


the  Teliost  or  Osseous  Fishes, — fishes  allied  to  the  perch, 
salmon,  pickerel,  etc.  They  occur  along  with  numerous 
Sharks  of  both  ancient  and  modern  types  (Cestracionts  and 


CRETACEOUS   PERIOD.  195 

Squalodonts),  and  many  also  of  Ganoids.  Thus  the  ancient 
and  modern  forms  of  Fishes  were  united  in  the  population 
of  the  Cretaceous  seas,  the  former,  however,  making  hardly 
more  than  a  tenth  of  the  species.  Fig.  329  represents  one 
of  these  Teliost  Fishes,  related  to  the  Salmon  and  Smelt,  from 
the  Chalk  at  Lewes,  England.  There  were  also  Herring, 
and  many  other  kinds. 

The  Eeptiles  included  species  of  some  of  the  Jurassic 
genera,  as  Pterodactyls,  Ichthyosaurs,  Plesiosaurs,  and  the 


Fig.  330. 


Mosasaurus  Ilofmanni  (X  A). 

Iguanodon  ;  also  of  other  genera,  as  Mosasaurs  (fig.  330),  and 
true  Crocodiles. 

No  remains  of  Mammals  or  Birds  have  yet  been  gathered 
from  the  Cretaceous  formation. 

3.  General  Observations. 

1.  Geography. — In  North  America  the  position  of  th«» 
Cretaceous  beds  along  the  borders  of  the  Atlantic  south  of 
New  York,  near  the  Mexican  Gulf,  and  also  over  a  large  part 
of  the  Eocky  Mountain  region,  indicates  that  these  border 


196 


MESOZOIC    TIME — REPTILIAN   AGE. 


regions  and  the  Western  Interior  were  under  water  when 
the  period  opened,  as  represented  in  the  following  map  (fig. 
331).  The  shaded  part  of  the  continent  exhibits  the  extent 
to  which  it  was  submerged.  (This  map  should  be  compared 
with  that  on  page  73).  It  shows  that  the  Chesapeake  and 
Delaware  Gulfs  were  in  the  ocean ;  that  Florida  was  still  under 
water  j  that  the  region  of  the  Missouri  Eiver  was  a  salt- 
Fig.  SSL 


North  America  in  the  Cretaceous  Period  ;  MO,  Upper  Missouri  region. 

water  region;  that  in  fact  the  Rocky  Mountains  were  at 
least  6000  or  7000  feet  lower  than  now,  the  Cretaceous  beds 
having  now  this  elevation  upon  them.  The  Mexican  Gulf 
spread  over  a  large  part  of  Georgia,  Alabama,  and  Missis- 
sippi, extended  northward  to  the  mouth  of  the  Ohio,  and 


CRETACEOUS   PERIOD.  197 

then  west  of  Missouri  and  Kansas  stretched  far  north  over 
the  present  slopes  of  the  great  Western  mountains,  reaching 
perhaps  to  the  Arctic,  though  on  this  point  the  evidence  is 
not  yet  decisive.  The  deposits,  excepting  those  of  Texas, 
appear  to  be  of  seashore  and  off-shore  formations;  the 
Texlm  compact  limestones  were  probably  formed  in  clear 
interior  waters. 

In  Europe  the  Chalk  appears  to  have  been  accumulated 
in  an  open  sea,  where  the  water  was  one  or  more  hundred 
feet  deep.  The  material  of  the  Chalk  has  been  stated  on 
page  190  to  be  mainly  the  shells  of  Ehizopods,  and  thai  of 
the  associated  flint  to  have  been  derived  from  Diatoms  and 
Sponges.  Ehizopods  and  Diatom  >  are  now  living  in  many 
parts  of  the  ocean,  over  the  bottom,  even  where  the  depth 
is  thousands  of  feet,  and  are  making  accumulations  of  vast 
area.  There  appear,  hence,  to  be  in  the  present  seas  the 
conditions  requisite  for  making  chalk  and  also  flint.  The 
many  Sponges,  Echini,  and  Shells  found  in  the  Chalk  beds 
are  evidence,  however,  that  the  depth  was  not  thousands  of 
feet,  although  it  may  have  been  a  few  hundreds.  The  fossils 
of  the  Chalk  are  in  many  regions  turned  into  flint,  and  some 
hollow  specimens  are  filled  with  quartz-crystals,  or  agate 

2.  Climate. — The  corals  and  other  tropical  life  of  the  Bri- 
tish rocks  indicate  that  the  seas  were  at  least  warm-tem- 
perate to  latitude  60°  north  on  the  east  side  of  the  ocean. 
On  the  American  side  it  appears  to  have  been  cooler,  as  it 
now  is,  in  corresponding  latitudes;  and  still  the  temperature 
was  considerably  warmer  than  the  present.  The  warm 
oceanic  zone  which  spread  over  the  British  seas  appears, 
from  the  distribution  of  the  fossils,  to  have  reached  the 
North  American  coast  south  of  Long  Island,  and  perhaps 
had  no  place  on  the  coast  north  of  Cape  Hatteras.  The 
plants  of  the  Upper  Missouri  region  indicate  a  warm-tern- 
perate  climate  ever  that  territory. 


198  MESOZOIC   TIME. 


1.  Time-Ratios. — The  ratios  between  the  Paleozoic  ages  as 
to  the  length  of  time  that  elapsed  during  their  progress,  or 
their  time-ratios,  are  stated  on  p.  145  as  probably  not  far 
from  3:1:1. 

The  American  Mesozoic  formations  are  too  imperfect  to 
be  used  as  data  for  calculating  the  Mesozoic  time-ratios;  and 
in  Europe  there  is  much  uncertainty  as  to  the  actual  thick- 
ness of  the  rocks.  Calculating  from  the  best  estimates  of 
the  thickness  which  have  been  given,  the  time-ratio  between 
the  Paleozoic  and  Mesozoic  is  nearly  3£:1;  and  between 
the  Triassic,  Jurassic,  and  Cretaceous  periods,  1:1^:1. 
That  is,  Mesozoic  time  was  hardly  one-third  as  long  as  the 
Paleozoic ;  and  the  three  periods  of  the  Mesozoic  were  not 
far  from  equal,  the  Jurassic  being  one-quarter  the  longest. 

2.  American  Geography. — On  page  162  it  is  remarked  that 
the  Mesozoic  formations  were  confined  to  the  Atlantic  and 
Gulf  border  regions,  and  to  an  interior  region  west  of  the 
Mississippi  covering  much  of  the  Eocky  Mountain  area,  and 
that  the  intermediate  portion  of  the  continent  had  probably 
become  part  of  the  dry  land.     The  facts  which  have  been 
presented  in  the  preceding  pages  have  sustained  this  state- 
ment.    The  Triassico-Jurassic   beds,   as   has   been   shown, 
lie  in  long  rfarrow  strips  between  the  Appalachians  and  the 
coast,  and  spread  widely  over  the  Eocky  Mountain  region. 
The  Cretaceous  beds  cover  the  Atlantic  and  Gulf  borders, 
and  also,  like  the  Triassic,  a  very  large  part  of  the  slopes 
of  the  Eocky  Mountains.    The  eastern  half  of  the  continent 
during  the  Mesozoic  was,  therefore,  receiving  rock-forma- 
tions only  along  its  borders,  while  the  western  half  had 
marine  deposits  in  progress  over  its  great  interior.     None 
of  the  American  Mesozoic  deposits  bear  any  evidence  that 
they  were  formed  in  a  deep  ocean.     They  appear  to  have 
been  formed  along  coasts,  or  in  shallow  waters  off  coasts,  or 


REPTILIAN    AGE.  199 

in  shallow  inland  seas;  and  only  the  Cretaceous  limestone 
of  Texas  indicates  a  pure  open,  though  not  deep,  sea,  like 
that  required  for  coral-reefs. 

The  Appalachians — the  eastern  mountains  of  the  continent 
— had  nearly  their  present  elevation  before  the  early  Mcso- 
zoic  beds  commenced  to  form  (p.  185).  But  the  region  of 
the  Eocky  Mountains — the  western  chain — was  to  a  great 
extent  still  a  shallow  sea  even  during  the  Cretaceous  period, 
or  when  the  Mesozoic  era  was  drawing  to  its  close  (p.  197). 

Only  one  series  of  mountain-elevations  can  be  pointed 
out,  with  our  present  knowledge,  as  originating  in  eastern 
North  America  in  the  course  of  the  Mesozoic  era,  although 
great  oscillations  of  level  were  much  of  the  time  in  progress 
(p.  185).  This  one  is  that  of , the  Mesozoic  red  sandstone 
and  trap  along  the  Atlantic  border  region.  The  trap  ridges, 
ranging  through  the  Connecticut  valley  from  New  Haven, 
Ct.,  to  northern  Massachusetts,  that  of  the  Palisades  on  the 
Hudson,  and  those  connected  with  the  early  Mesozoic  rocks 
of  New  Jersey,  Pennsylvania,  Virginia,  North  Carolina, 
and  Nova  Scotia,  appear  to  date  from  a  common  epoch 
(p.  185).  They  conform  to  a  common  system,  being  parallel 
to  the  Appalachian  chain  through  its  varying  courses,  and 
not  following  one  special  compass-course.  The  epoch  of 
their  formation  probably  divides  off  the  Triassico-Jurassic 
period  of  North  America  from  the  Cretaceous. 

The  study  of  the  Pacific  border  of  the  continent  will 
probably  make  known  one  or  more  additional  mountain- 
ranges  of  Mesozoic  origin. 

3.  European  Geography. — Europe  has  its  Mesozoic  rocks 
distributed  in  patches,  or  in  several  independent  or  nearly 
independent  areas,  which  show  that  it  retained  its  condition 
of  an  archipelago  throughout  Mesozoic  time.  The  oscilla- 
tions of  level,  as  indicated  by  the  variations  in  the  rocks, — 
variations  both  as  to  the  nature  of  the  beds  and  their  distri- 
bution,— were  more  numerous  and  irregular  than  in  Nortb 

18 


200  MESOZOIC    TIME. 

America.  The  mountain-elevations  formed,  however,  were 
few  and  small  compared  with  those  that  followed  either  the 
Paleozoic  or  Mesozoic  era.  One  series  of  disturbances  is 
referred  to  the  close  of  the  Triassic,  and  another  to  the  close 
of  the  Jurassic. 

Among  the  Mesozoic  formations  of  the  European  conti- 
nent there  are  deposits  of  all  kinds, — those  of  seashores;  of 
off-shore  shallow  waters ;  of  inland  seas ;  of  moderately  deep 
oceanic  waters;  and  of  marshy,  or  dry  and  forest-covered, 
land. 

Both  in  America  and  Europe  there  were  some  coal-beds 
made,  though  of  small  extent  compared  with  those  of  the 
Carboniferous  age 

4.  Life. — The  Mesozoic  era  witnessed — (1)  the  decline  of 
some  ancient,  or  Paleozoic,  types,  of  both  plants  and  animals, 
(2)  the  increase  and  culmination  of  medieval  or  Mesozoic 
types,  and  (3)  the  beginning  of  some  of  the  most  important 
of  modern  or  Cenozoic  types. 

(1.)  Disappearance  of  Ancient  or  Paleozoic  features. — Among 
the  ancient  tribes  of  plants  the  Calamites,  or  tree-rushes,  and 
several  genera  of  Ferns,  disappear  in  the  Jurassic.  Among 
the  old  Brachiopod  tribes  the  Spirifer  and  Leptcena  families 
end  in  the  Triassic ;  and  among  higher  Mollusks  the  Silu- 
rian type  of  Orthoceras,  and  Devonian  of  .Goniatites,  have 
their  last  species  in  the  Triassic. 

(2.)  Progress  in  Mesozoic  features. — The  Cycads,  among 
plants,  were  those  most  characteristic  of  the  Mesozoic :  they 
afterwards  yield  to  other  kinds,  and  are  now  nearly  an 
extinct  tribe.  The  Cephalopods,  among  Mollusks,  existed 
in  vast  numbers,  both  those  with  external  shells,  as  the 
Ammonites,  and  those  without,  as  the  Belemnites.  The  whole 
number  of  species  of  Cephalopods  now  known  from  the 
Mesozoic  formations  is  nearly  1200.  Of  these,  about  950 
were  of  the  Nautilus  and  Ammonite  families.  Since  the 
Cretaceous  period  no  Ammonite  has  existed,  and  at  the 


REPTILIAN    AGE.  201 

present  time  there  are  only  2  or  3  species  of  Nautilus.  The 
whole  number  of  species  of  Cephalopoda  living  in  the  courso 
of  the  Mesozoic  era  may  have  been  three  or  four  times  1200, 
as  only  a  part  would  have  been  preserved  as  fossils.  The  sub- 
kingdom  of  Mollusks,  therefore,  culminated  in  the  Mesozoie 
era ;  for  its  highest  order,  that  of  the  Cephalopods,  was  then 
at  its  maximum. 

The  type  of  Reptiles  was  another  that  expanded  and 
reached  its  height — that  is,  its  maximum  in  number,  variety, 
and  rank  of  species — and  commenced  its  decline  in  the 
Mesozoic  era. 

There  were  huge  swimming  Saurians,  Enaliosaurs,  in  the 
place  of  whales  in  the  sea;  bat-like  Saurians  or  Pterodac- 
tyls flying  through  the  air;  and  four-footed  Saurians,  both 
grazing  and  carnivorous,  many  of  them  25  to  50  feet  long, 
occupying  the  marshes  and  estuaries.  In  the  era  of  the 
"VYealden  and  Lower  Cretaceous  there  lived,  in  and  about 
Great  Britain,  4  or  5  species  of  Dinosaurs  20  to  50  feet  long, 
10  to  12  Crocodilians,  Lizards,  and  Enaliosaurs  10  to  50  or 
60  feet  long,  besides  Pterodactyls  and  Turtles;  and  many 
more  than  this,  since  all  that  lived  would  not  have  left  their 
remains  in  the  deposits.  To  appreciate  this  peculiarity  of 
medieval  time,  it  should  be  considered  that  in  the  present 
ago  Britain  has  no  large  Eeptiles;  in  Asia  there  are  only 
two  species  over  15  feet  in  length;  in  Africa  but  one;  in  all 
America  but  three;  in  the  whole  world  not  more  than  six; 
and  the  largest  of  the  six  does  not  exceed  25  feet  in  length. 
The  Mesozoie  era  is  well  named  the  Age  of  Reptiles. 

All  the  Mesozoic  animals,  excepting  the  Mammals,  belong 
to  the  Oviparous  divisions;  and  the  Mammals  were  mainly 
Marsupial  species, — that  is,  semi-oviparous  Mammals,  as 
explained  on  p.  50,  —  species  quite  in  harmony,  therefore, 
with  the  other  life  of  the  era.  The  Birds  of  the  age,  or  at 
least  some  of  them,  partook  of  the  reptilian  features  of  the 
time,  having  long  tails  like  the  associated  Reptiles  (though 


202  MESOZOIC   TIME. 

feathered  tails),  and  possessing  some  other  peculiarities  of 
the  scaly  tribes.  The  long-tailed  birds  and  Pterodactyls 
were  the  flying  creatures  of  the  age;  the  Ichthyosaurs 
and  Plesiosaurs,  and  the  like,  the  "great  whales;"  the 
Telcosaurs,  Iguanodon,  and  other  gigantic  species  of  the 
estuaries  and  marshes,  the  creeping  species.  These,  along 
with  the  small  Marsupials  and  Insectivores  of  the  Cycadean 
and  Coniferous  forests,  were  the  more  prominent  kinds  of 
Mesozoic  life. 

(3.)  Introduction  of  Cenozoic  features. — Among  Plants  the 
first  of  Angiosperms,  (or  the  order  including  all  trees  having 
a  bark  (Oak,  Maple,  Apple,  &c.),  excepting  the  Conifers)  and 
the  first  of  Palms,  are  found  in  the  Cretaceous.  These 
become  the  characteristic  plants  of  the  Cenozoic  era  and 
Age  of  Man. 

Among  Vertebrates  there  were  the  first  of  the  great  order 
of  Teliost  or  Osseous  Fishes  in  the  Cretaceous  (p.  194),  all 
previous  species  being  either  Selachians  (Shark  tribe)  or 
Ganoids;  the  first  of  the  modern  tribe  of  Sharks  in  the 
Jurassic ;  the  first  of  the  modern  genus  of  Crocodilus  in  the 
Jurassic;  the  first  of  Birds  in  the  Triassic  or  Jurassic, — tho 
reptilian  Birds;  the  first  of  Mammals  in  the  Triassic, — 
Marsupials,  or  semi-oviparous  Mammals,  along  with  some 
Insectivores. 

Of  the  classes  of  Vertebrates,  Fishes  and  Eeptiles  com- 
mence in  the  middle  and  later  Paleozoic,  and  Birds  and 
Mammals  in  the  early  or  middle  Mesozoic. 

DISTURBANCES  AND  CHANGES  OP  LEVEL   CLOSING   MESOZOIC 
TIME. 

At  the  close  of  the  last  period  of  the  Mesozoic  era — the 
Cretaceous — there  was  an  extermination  of  the  species  then 
on  the  globe,  which  was  as  complete  as  that  closing  the 
Paleozoic  era.  No  species  have  yet  been  proved  to  have 
survived  from  the  Cretaceous  into  the  Cenozoic  era,  except 


REPTILIAN    AGE.  203 

possibly  some  kinds  of  Sharks.  The  species  most  likely  to  have 
outlived  the  period  of  disturbance  which  intervened  are  the 
species  of  the  open  ocean,  as  Sharks,  since  variations  in  the 
climate  of  the  globe  and  changes  of  level  over  its  surface 
affect  but  slightly  the  ocean's  waters  remote  from  coasts. 

Besides  the  destruction  of  species,  there  was  the  final 
extinction  of  several  families  and  tribes.  The  great  family 
of  Ammonites,  and  many  others  of  Mollusks,  all  the  genera 
of  Reptiles  excepting  Crocodilus,  and  others  in  all  depart- 
ments of  life,  came  to  their  end  in  the  revolution. 

From  the  occurrence  of  Cretaceous  rocks  in  the  structure 
of  mountains  or  about  their  tops,  and  the  existence  of 
marine  rocks  of  the  next  (or  Tertiary)  period  only  at  low 
levels  upon  the  sides,  or  towards  the  foot,  of  the  same  moun- 
tains, it  has  been  discovered  that  the  epoch  of  disturbance 
or  revolution  was  remarkable  for  the  number  of  great  moun- 
tain-ranges which  either  began  at  that  time  their  existence 
above  the  oceans,  or  else  had  their  altitude  greatly  increased. 
The  region  occupied  by  a  Cretaceous  sea  must  have  been 
raised  into  a  mountain-elevation  before  seashore  Tertiary 
strata  could  have  been  formed  about  its  base.  The  Eocky 
Mountains  and  Andes,  Himalayas  and  Alps,  received  a  large 
part  of  their  elevation  subsequent  to  the  Mesozoic  era,  and 
some  considerable  part  immediately  at  the  close  of  the  Cre- 
taceous period,  although  the  elevation  in  the  case  of  each 
of  these  great  chains  of  the  world  was  continued  in  progress 
through  the  Tertiary  and  afterwards. 

The  Himalayas  have  no  known  Cretaceous  rocks  in  tbeir 
structure  j  but  Oolitic  beds  occur  at  a  height  of  14,000  to 
18,000  feet,  and  extend  along  at  these  elevations  for  400 
miles.  (Strachey.)  The  land  may  in  part  have  made  its 
emergence  from  the  sea  before  the  Cretaceous  period  began; 
whether  so  or  not,  it  continued  long  after  rising :  the  eleva- 
tion of  the  western  part  of  the  chain  about  Cashmeer  was 
not  completed  until  after  the  Tertiary  period  had  well 


204  MESOZOIC   TIME. 

advanced.  The  Apennines  began  their  elevation  about  the 
middle  of  the  Cretaceous  period,  but  made  the  most  of  their 
altitude  in  the  early  Tertiary.  The  Andes  have  Cretaceo- 
oolitic  beds  about  their  higher  slopes,  proving  also  their 
elevation  to  have  been  essentially  cotemporaneous  with  that 
of  the  Eocky  Mountains  and  other  highest  mountains  of 
the  globe. 

The  facts  will  be  better  appreciated  after  a  study  of  the 
Tertiary  formations,  which  afford  part  of  the  evidence  on 
which  these  conclusions  are  based. 

Extermination  of  life. — The  proofs  of  elevation  are  so 
many  and  so  extensive  that  it  is  reasonable  to  infer  that  a 
great  change  of  climate  must  also  have  taken  place  over 
the  globe.  The  Arctic  regions  may  have  been  elevated 
more  than  lower  latitudes,  for  Tertiary  rocks  do  not  occur 
on  the  eastern  borders  of  the  American  continent  north  of 
the  parallel  of  42°  N.  to  show  that  the  continent  was  then 
below  its  present  level.  The  change  of  climate  consequent 
on  the  increase  of  Arctic  lands,  and  the  increased  number  and 
height  of  mountain-chains,  may,  therefore,  have  been  so 
great  as  to  have  proved  a  principal  cause  of  the  extinction 
of  life  that  then  took  place  both  over  the  land  and  along 
the  oceanic  borders.  Should  the  cold  winds  and  cold  oceanic 
currents  of  the  northern  part  of  the  existing  temperate 
zone  penetrate  for  a  single  year  into  the  tropical  regions, 
they  would  produce  a  general  extermination  of  the  plants 
and  animals  of  the  land,  and  also  of  those  of  the  coast  and 
sea-borders,  even  to  a  great  depth,  as  far  as  the  cold  oceanic 
currents  extended.  If  a  change  of  climate  took  place  at 
the  close  of  the  Cretaceous,  such  as  has  been  supposed,  these 
very  results  would  then  have  happened;  moreover,  the 
frigid  air  and  waters  would  have  found  tropical  life  much 
nearer  to  the  pole  than  now,  even  over  Europe  and  a  largo 
part  of  the  United  States. 


CENOZOIC   TIME. 


IV.  CENOZOIC  TIME. 

1.  Age  of  Mammals. — Cenozoic  time  covers  but  one  age, — 
the  age  of  Mammals. 

2.  General  characteristics. — In  the  transition  to  this  age 
the  life  of  the  world  takes  on  a  new  aspect.     Trees  of 
modern  types — Oak,  Maple,  Beech,  etc.,  and  Palms — unite 
with   Conifers   to   make   the   forests;    Mammals   of  great 
variety  and  size — Herbivores,  Carnivores,  and  others,  suc- 
cessors to  the  small  semi-oviparous  Mammals  and  Insect- 
ivores — tenant  the  land   in   place  of  Reptiles;  true  Birds 
and  Bats  possess  the  air  in  place  of  reptilian  Birds  and 
Pterodactyls ;  Whales  and  Teliost  or  common  Fishes,  with 
Sharks,  mainly  of  modern  type,  occupy  the  waters  in  place 
of  Enaliosaurs,  and  almost  to  the  exclusion  of  the  ancient 
tribes  of  Cestraciont  Sharks  and  Ganoids. 

It  has  already  been  shown  that  several  of  these  modern- 
izing features  began  to  appear  in  the  Mesozoic  era.  Thus, 
in  all  geological  as  well  as  other  history  (as  remarked  on 
page  154),  every  age  has  preparations  for  it  in  progress  in 
the  age  preceding.  There  are  no  abrupt  transitions. 
The  Mammals,  Birds,  Teliosts,  and  Angiosperms  of  the 
Reptile  world  were  precursors  of  a  future  and  brighter  era, 
when  these  species  should  be  the  predominant  races.  The 
type  of  Mammals  appears  in  Cenozoic  time  under  several 
successive  faunas  of  different  species,  each  successively 
exterminated,  and  finally  expands  till  in  number  of  kinds 
and  in  the  magnitude  of  its  wild  beasts  the  Mammalian  age 
far  exceeds  the  Age  of  Man.  These,  also,  disappear  before 
the  last  age  opens  and  during  its  early  progresa 

MAMMALIAN  AGE. 

The  age  of  Mammals  is  divided  into  two  Periods:—!. 
The  Tertiary;  2.  The  Post-tertiary. 


206  CENOZOIC   TIME — MAMMALIAN    AGE. 

In  the  Tertiary  the  Mammals  are  all  extinct  species,  and 
the  other  species  of  life  mostly  so ;  the  number  of  living 
species  of  Invertebrates  (Eadiates,  Mollusks,  and  Articu- 
lates) varies  from  none  in  the  early  part  of  the  period  to  90 
per  cent,  in  the  latter  part. 

In  the  Post-tertiary  the  Mammals  are  nearly  all  of  extinct 
species,  but  the  Invertebrates  are  almost  wholly  of  living 
species,  not  over  5  per  cent,  being  extinct. 

I.  TERTIARY  PERIOD. 

1.  Epochs. 

The  beds  of  the  Tertiary  period  have  been  divided  by 
Lyell  into  three  series : — 

1.  EOCENE  (from  the  Greek  eos,  dawn,  and  kainos,  recent). 
Species  all  extinct. 

2.  MIOCENE  (from  meion,  less,  and  kainos~) :  15  to  40  per 
cent,  of  the  species  extinct. 

3.  PLIOCENE  (from  pleion,  more,  and  kainos)  :  50  to  90  per 
cent,  of  the  species  extinct. 

These  subdivisions  do  not  correspond  to  the  epochs  of  the 
period,  either  in  Europe  or  America,  although  affording 
convenient  terms  for  Lower,  Upper,  and  Middle  Tertiary. 

In  North  America  the  epochs  are  the  following: — 

1.  CLAIBORNE,  or  that  of  the  Tertiary  beds  of  Claiborne, 
Alabama, — the  early  Eocene. 

2.  JACKSON,  or  that  of  the  beds  of  Jackson,  Mississippi, — 
the  Middle  Eocene. 

3.  VICKSBURQ,  or  that  of  the  beds  of  Vicksburg,  Missis- 
sippi,— the  later  Eocene. 

4.  YORKTOWN,  or  that  of  the  beds  of  Yorktown,  Virginia, 
in  which  15  to  30  per  cent,  of  the  species  are  living, — usually 
called  Miocene,  but  probably  including  part,  at  least,  of  the 
Pliocene. 

A -fifth -has  been  separated  as  Pliocene,  or  the  SUMTEII 
epoch,  based  on  observations  on  the  beds  in  Sumter  and 


TERTIARY    PERIOD.  207 

Darlington  districts,  South  Carolina;  but  it  is  probably  not 
distinct  from  the  Yorktown.  (Conrad.) 

2.  Rocks:  kinds  and  distribution. 

The  marine  Tertiaiy  beds  of  North  America  border  the 
continent  south  of  New  England  along  both  the  Atlantic 
Ocean  and  the  Mexican  Gulf,  like  the  Cretaceous.  They 
overlie  nearly  all  the  Cretaceous  beds  on  the  Atlantic 
border,  but  extend  less  far  inland  on  the  Gulf  border.  (See 
map  on  p.  69,  in  which  the  area  is  lined  obliquely  from  the 
left  above  to  the  right  below).  They  spread  northward 
along  the  Mississippi  to  the  mouth  of  the  Ohio,  and  also 
westward  beyond  this  river  into  Texas,  along  the  west  side 
of  the  Mexican  Gulf;  but  the  marine  Tertiary  beds  do  not, 
like  the  Cretaceous,  stretch  north  over  the  Eocky  Mountain 
region.  There  arc,  however,  about  the  Upper  Missouri  and 
over  other  parts  of  the  slopes  of  these  mountains,  extensive 
deposits  of  fresh-water  Tertiary,  the  lowest  layers  of  which 
are  of  brackish-water  origin.  (On  the  map  the  area  of  this 
fresh-water  Tertiary  is  distinguished  by  being  more  openly 
lined  than  those  of  the  marine  Tertiary.)  The  most  northern 
locality  of  Tertiary  on  the  Atlantic  coast  is  on  Martha's 
Vineyard.  The  Tertiary  formation  also  occurs  extensively 
in  California  and  Oregon,  and  in  some  places  has  a  height 
of  2000  feet  above  the  sea. 

The  Eocene  beds  are  best  displayed  in  the  Tertiary  of  the 
Gulf  border  from  the  Mississippi  River  to  South  Carolina, 
and  the  marine  Miocene  beds  on  the  Atlantic  border  from 
New  Jersey  to  South  Carolina,  though  both  occur  in  other 
parts  of  the  Tertiary  region.  The  fresh-water  Tertiary  of 
the  Upper  Missouri  is  at  its  base  probably  Eocene;  it  con- 
tains much  lignite  and  many  fossil  leaves,  like  the  lower 
Eocene  elsewhere.  The  rest  is  Miocene  and  Pliocene. 

The  Tertiary  beds  are  generally  but  little  consolidated: 
Lhey  consist  of  compacted  sand,  pebbles,  clay,  earth  that 


208  CENOZOIC   TIME — MAMMALIAN   AGE. 

was  onco  the  mud  of  the  sea-bottom  or  of  estuaries,  mixed 
often  with  shells, — being  just  such  kinds  of  deposits  as  are  now 
forming  along  the  seashores  and  in  the  shallow  bays  and 
estuaries  of  the  coast,  or  in  the  shallow  waters  off  the  coast. 
There  are  also  some  limestones  made  of  shells ;  and  others 
made  of  corals,  resembling  the  reef-rock  of  coral  seas.  The 
latter  are  found  mainly  in  the  States  bordering  on  the 
Mexican  Gulf.  Another  variety  of  rock  is  the  buhrstone,  a 
very  cellular  siliceous  rock,  flinty  in  texture,  used,  on  account 
of  its  being  so  hard  and  at  the  same  time  full  of  irregu- 
lar cavities,  for  making  mill-stones.  It  is  found  in  South 
Carolina. 

The  Tertiary  of  Great  Britain  occurs  mostly  in  the  south- 
eastern part  of  England,  in  the  London  basin  as  it  is  called, 
and  on  the  southern  and  eastern  borders  of  the  island, 
adjoining  the  Cretaceous. 

On  the  continent  of  Europe  the  Paris  basin  is  noted  for 
its  Eocene  strata  and  fossil  Mammals.  Other  Tertiary 
areas  are  those  of  the  Pyrenean  and  Mediterranean  regions, 
those  of  Switzerland,  of  Austria,  etc.  Some  of  the  marine 
Eocene  beds  contain  a  fossil  having  the  shape  of  a  coin, 
called  a  Nummulite  (from  the  Latin  nummus,  a  cotVi).  One 
is  figured  on  page  59.  Occasionally  the  beds  are  so  far 
made  up  of  these  Nummulites  that  they  are  called  Nummu- 
litic  limestone. 

These  marine  Eocene  strata  spread  very  widely  over  both 
Europe,  northern  Africa,  and  Asia, — occurring  in  the  Pyre- 
nees, forming  some  of  their  summits;  in  the  Alps  to  a  height 
of  10,000  feet;  in  the  Carpathians,  in  Algeria,  in  Egypt,  where 
the  most  noted  pyramids  are  made  of  Nummulitic  limestone, 
in  Persia,  in  the  western  Himalayas  (the  region  of  Cash- 
mere), to  a  height  of  15,000  feet.  The  later  Tertiary  forma- 
tions are  much  more  limited  in  distribution,  and  many  are 
of  terrestrial  or  fresh-water  origin. 

The  rocks  are  similar  to  those  of  North  America,  but 


TERTIARY    PERIOD.  209 

with  more  of  compact  sandstone  and  compact  limestone. 
The  sandstone  is  a  very  common  building-stone  in  different 
parts  of  Europe,  being  soft  enough  to  be  worked  with  faci- 
lity, yet  generally  hardening  on  exposure,  owing  to  the  fact 
that  it  contains  calcareous  particles  (triturated  shells), 
which  render  the  percolating  waters  or  rain  calcareous,  so 
that  on  evaporating  they  produce  a  calcareous  deposit,  as  a 
cement,  among  the  grains  of  sand. 

The  Eocene  formation  of  southeastern  England  consists  of 
beds  of  clay  and  sand,  the  lowest  of  sand  sometimes  con- 
taining rolled  flints.  The  Lower  Eocene  includes  the  Thanet 
sands,  Woolwich  beds,  London  clay,  and  Bognor  beds ;  the 
Middle  Eocene,  the  Bagshot  beds,  Hcadon  group,  and  others; 
the  Upper  Eocene,  the  Hempstead  beds  near  Yarmouth.  The 
Older  Pliocene  includes  the  Coralline  crag  and  Eed  crag  of 
Suffolk;  and  the  Newer  Pliocene,  the  Norwich  crag,  which 
is  of  flnvio-marino  origin.  No  marine  Miocene  beds  have 
yet  been  identified  in  Great  Britain. 

3.  Life. 

1.  Plants.    * 

The  great  feature  of  the  vegetation  is  the  prevalence  of 
the  class  of  Angiosperms,  which  made  its  first  appearance 
in  the  Cretaceous.  Leaves  of  Oak,  Poplar,  Maple,  Hickory, 
Dogwood,  Mulberry,  Magnolia,  Cinnamon,  Fig,  Sycamore,  and 
many  others,  have  already  been  found  in  both  American 
and  European  Tertiary  strata,  besides  the  remains  of  Palms 
and  Conifers.  A  leaf  of  a  Tertiary  Fan-palm  (species  of 
Sabal)  found  in  the  Upper  Missouri  must  have  been,  when 
entire,  12  feet  in  breadth.  Nuts  are  also  common  in  some 
beds, — as  at  Brandon,  Vermont.  Fig.  332  is  the  leaf  of  an 
Oak ;  fig.  333,  of  a  species  of  Cinnamon ;  fig.  334,  of  a  Palm ; 
fig.  335,  the  nut  of  a  beech,  closely  like  that  of  the  common 
beech ;  fig.  336,  another  nut,  from  Brandon,  of  unknown 
relations. 


210 


CENOZOIC   TIME — MAMMALIAN   AGE. 


The  Eocene  Plants  in  central  and  southern  Europe  have, 
in  general,  a  striking  resemblance  to  those  of  Australia,  and 
the  Miocene  and  Pliocene  to  those  of  America.  The  forests 
of  England,  in  the  Eocene,  abounded  in  Palms. 

The  microscopic  plants  which  form  siliceous  shells  called 
Diatoms  (p.  61)  make  extensive  deposits  in  some  places. 

Figs.  332-336. 
S3 


Kg.  332,  Quercus  myrtifolia?;  333,  Cinnamomnm  Missisuippiense ;  334,  Calamopsis  Dan»; 
335,  Fagus  ferruginea? ;  336,  Carpolithes  irregularis. 

One  stratum  near  Eichmond,  Virginia,  is  30  feet  thick,  and 
is  many  miles  in  extent ;  and  another,  near  Bilin  in  Bohe- 
mia, is  14  feet  thick.  The  material  from  the  latter  place 
was  used  as  a  polishing-powder  (and  called  Tripoli,  or 
polishing-slate)  long  before  it  was  known  that  its  fine  grit 
was  owing  to  the  remains  of  microscopic  life.  Ehrenberg 


TERTIARY    PERIOD. 


211 


has  calculated  that  a  cubic  inch  of  the  fine  earthy  slate  con- 
tains about  forty-one  thousand  millions  of  organisms. 

2.  Animals. 

The  most  prominent  fact  with  regard  to  the  Tertiary 
Invertebrates  is  their  general  resemblance  to  modern 
species.  Although  a  number  of  the  genera  are  extinct,  and 
all  the  Eocene  species,  there  is  still  a  modern  look  in  the 
remains,  and  the  specimens  have  often  the  freshness  of  a 
shell  from  a  modern  beach. 

The  species  of  Tertiary  shells  found  in  the  European  beds 
number  about  6000;  while  not  over  3000  have  been  gathered 
from  the  North  American  beds. 

The  following  are  figures  of  a  few  species  of  the  Clai- 
borne  epoch.  Fig.  337  represents  an  Eocene  Oyster;  fig.  338, 


Figs.  337-341. 


MOLLUSKS:  Fig.  337,  Ostrea  selUeformis ;  338,  Crassatella  alta;  339,  Astarte  Conradi;  340, 
Cardita  planicosta;  341,  Turritella  carinata. 

a  species  of  Crassatella;  fig.  339,  an  Astarte;  fig.  340,  a  Car- 
dita; and  fig.  341,  a  Turritella:  all  are  from  Claiborne, 
Alabama. 

19 


212 


CENOZOIC   TIME — MAMMALIAN   AGE. 


Figures  342  to  345  are  of  species  of  shells  of  the  York- 
town  epoch,  from  Virginia;  figs.  342,  343  represent  a  very 


Figs.  342-345. 


GASTEBOPOD:   Figs.  342,  343,  Crepidula  costata.— CONCHIFERS  :   Fig.  344,  Yoldia  limatula 
345,  Callista  Sayana. 

common  Crepidula,  upper  and  under  sides.  The  species  of 
the  epoch  include  the  common  Oyster  and  Clam,  and  other 
modern  species ;  and  these  are,  therefore,  among  the  most 
ancient  of  living  species  on  the  globe;  for, until  the  Miocene 
epoch  opened,  every  species  of  Mollusk  that  had  existed  on 
the  globe  had  become  extinct,  and  every  species  of  other 
kinds  of  life,  if  we  except  some  Protozoans  and  Protophytes. 

With  regard  to  Vertebrates  the  points  of  special  interest 
are  the  following  : — 

1.  In  the  class  of  Fishes : — (1)  The  prevalence  of  Teliosts, 
or  fishes  allied  to  the  Perch  and  Salmon,  as  already  stated; 
and  (2)  the  abundance  of  Sharks,  some  of  them  having 
teeth  6  inches  long  and  broad.  The  teeth  of  sharks  are  the 
durable  part  of  the  skeleton ;  they  are  very  abundant  in 
both  Eocene  and  Miocene  beds.  Fig.  59,  p.  52,  represents 
a  tooth  of  the  Carcharodon  angustidens.  The  larger  teeth 
above  alluded  to  belong  to  the  Carcharodon  megalodon,  and 
are  found  at  different  places  on  the  Atlantic  border  from 
Martha's  Vineyard  south.  Fig.  58  represents  the  tooth  of 


TERTIARY   PERIOD.  213 

another  common  kind  of  Shark,  a  species  of  Lamna  (L. 
elegans),  from  Claiborne. 

In  the  class  of  Eeptiles:— The  existence  of  numerous 
Crocodiles  and  Turtles.  The  shell  of  one  of  the  Miocene  Tur- 
tles, found  fossil  in  India,  had  a  length  of  12  feet,  and  the 
animal  is  supposed  to  have  been  20  feet  long.  The  first  of 
Snakes,  moreover,  occur  in  the  Eocene. 

In  the  class  of  Birds :— The  species  found  are  not  reptilian 
or  long-tailed,  but  like  modern  birds;  they  are  related  to 
the  Pelican,  Waders,  Pheasants,  Perchers,  Vultures.  But  fossil  • 
birds  are  of  very  rare  occurrence;  none  have  yet  been  found 
in  America,  although  Mammalian  remains  are  common. 

In  the  class  of  Mammals  : — The  occurrence  of  the  first  of 
Whales,  the  first  of  Carnivores,  Herbivores,  Rodents,  Monkeys, 
and  of  other  tribes,  indicating  a  large  population  of  brute 
animals  wholly  different  from  the  present  in  species,  though, 
in  general,  related  to  the  modern  kinds  in  form  and  struc- 
ture. A  few,  however,  are  widely  diverse  from  any  thing 
in  existence, — such  combinations  as  the  mind  would  never 
have  imagined  without  aid  from  the  skeletons  furnished  by 
the  strata. 

In  the  early  Eocene  there  appear  to  have  been  more 
Herbivores  than  Carnivores;  but  afterward  the  Carni- 
vores were  as  common  as  now. 

Cuvier  first  made  known  to  science  the  existence  of  fossil 
Mammals.  The  remains  from  the  earthy  beds  about  Paris 
had  been  long  known,  and  were  thought  to  be  those  of 
modern  beasts.  But,  through  careful  study  and  comparisons 
with  living  animals,  he  was  enabled  to  bring  the  scattered 
bones  together  into  skeletons,  ascertain  the  tribe  to  which 
they  belonged,  and  determine  the  food  and  mode  of  life  of 
the  ancient  but  now  extinct  species.  Cuvier  acquired  his 
skill  by  observing  the  mutual  dependence  which  subsists 
between  all  parts  of  a  skeleton,  and,  in  fact,  all  parts  of 
an  animal.  A  sharp  claw  is  evidence  that  the  animal  has 


214 


CENOZOIC   TIME — MAMMALIAN    AGE. 


trenchant  or  cutting  molar  teeth,  and  is  a  flesh-eater;  a 
hoof,  that  he  has  broad  molars  and  is  a  grazing  species; 
and,  further,  every  bone  has  some  modification  showing  the 
group  of  species  to  which  it  belongs,  and  may  thus  be  an 
indication,  in  the  hands  of  one  well  versed  in  the  subject, 
of  the  special  type  of  the  animal,  and  of  its  structure,  even 
to  its  stomach  within  and  its  hide  without. 

One  of  these  Paris  beasts  is  called  a  Paleothere  (from  the 
Greek  palaios,  ancient,  and  therion,  wild  beast.  Its  form,  as 
restored,  is  shown  in  figure  346.  It  is  related  to  the  modern 
Tapir,  and  was  of  the  size  of  a  horse.  Another  kind,  called 

Fig.  346. 


Palseotherium  magnum. 

an  Anoplothere,  was  of  more  slender  habit,  and  somewhat 
resembled  a  stag.  There  were  others,  related  to  the  hog,  or 
Mexican  Peccary,  and  to  the  horse ;  also  some  Carnivores,  a 
Bat,  and  an  Opossum. 

The  only  American  Eocene  Mammals  that  have  been  dis- 
covered are  those  of  the  ocean,  as  "Whales.  The  bones 
of  a  species  of  whale,  called  a  Zeuglodon,  occur  in  many 
places  in  the  Gulf  States;  and  in  Alabama  the  vertebra 
were  formerly  so  abundant  as  to  have  been  built  up  into 


TERTIARY   PERIOD. 


215 


stone  walls,  or  burnt  to  rid  the  fields  of  them,  The  living 
animal  was  probably  70  feet  in  length.  One  of  the  larger 
vertebras  measures  a  foot  and  a  half  in  length  and  a  foot  in 
diameter. 

The  Miocene  beds  of  the  "  Bad  Lands"  on  the  White 
River,  in  the  Upper  Missouri  region,  have  afforded  remains 
of  a  large  number  of  Miocene  quadrupeds.  Among  them, 
according  to  Leidy,  there  are  eight  Carnivores  related 
somewhat  to  the  Hyena,  Dog,  and  Panther;  25  Herbivores, 
including  2  Rhinoceroses,  and  species  approaching  the  Tapir, 
Peccary,  Deer,  Camel,  Horse;  and  4  Eodents,  besides  many 

Fig.  347. 


Tooth  of  Titanotherium  Proutii  (X  %)• 

Turtles.  Figure  347  represents  a  tooth,  half  the  natural 
size,  of  a  Titanothere,  an  animal  related  to  the  Tapir  and 
Paleothere,  but  of  elephantine  size,  standing  probably  7  or 

Fig.  348. 


Teeth  of  Rhinoceros  Nebrasce 


8  feet  high.     Figure  348  represents 
one  of  the  Rhinoceroses. 

19* 


few  of  the  teeth  of 


216 


CENOZOIC   TIME — MAMMALIAN   AGE. 


Fig.  349. 


Among  Mammals  of  the  European  Miocene  there  were 
Elephants,  Mastodons,  Deer,  and  other  Herbivores,  many 
Carnivores,  Monkeys,  Ant-eaters,  etc.  One  of  the  most  sin- 
gular species  is  the  Dinothere,  the  form  of  the  skull  of  which 
— the  only  part  of  the  skeleton  found — is  shown  in  the 
annexed  figure;  its  actual 
length  is  3  feet  8  inches.  It 
appears  to  have  had  a  pro- 
boscis like  an  Elephant,  but 
the  tusks  proceeded  from  the 
lower  instead  of  upper  jaw,  and 
were  bent  downward.  Some  sup- 
pose it  to  have  been  related  to 
the  Elephant,  and  others  to  the 
marine  Manatus  and  Dugong. 

In  fresh-water  Pliocene  beds 
of  the  Upper  Missouri  there  are 
remains  of  a  fauna  totally  dif- 
ferent in  species  from  that  of 
the  Miocene.  It  included  a  Rhinoceros,  an  Elephant  of  great 
size,  a  Mastodon,  3  species  of  Camel,  4  of  the  Horse  family, 
Deers,  a  Wolf,  a  Fox,  a  Beaver,  and  a  Porcupine,  all  of 
extinct  species;  it  had,  in  its  Camels  and  Ehinoceros  and 
Elephant,  quite  an  Oriental  character,  as  Leidy  observes, 
though  still  prominently  North  American  in  the  preponder- 
ance of  Ungulates,  and  the  absence  of  the  South  American 
type  of  Edentates  or  Sloths. 

The  earliest  of  the  Bovine  or  Ox  group  occur  in  the 
European  Pliocene. 

4.  General  Observations. 

1.  Geography. — The  Tertiary  period  completed  mainly  the 
work  of  rock-making,  along  the  borders  of  the  continent, 
which  had  been  in  progress  during  the  Cretaceous  period. 
The  accompanying  map  shows  approximately  the  part  of 


Dinotherium  giganteum 


TERTIARY   PERIOD. 


217 


the  continent  of  North  America  under  the  sea  when  the 
Tertiary  era  began.     By  comparing  it  with  the  map  of  the 

Fig.  350. 


Map  of  North  America  in  the  early  part  of  the  Tertiary  Period. 

Cretaceous  continent,  p.  196,  it  is  seen  that  the  Rocky 
Mountain  region  had  become  dry  land  in  the  interval;  but, 
as  Ilayden  has  shown  by  the  discovery  of  brackish-water 
beds  in  the  lowest  Tertiary  of  the  Upper  Missouri  region, 
the  elevation  was  at  first  small;  and  its  present  height  was 
gradually  attained  later  in  the  Tertiary  period.  The  great 
river-system  of  the  Mississippi,  embracing  slopes  from  the 
Rocky  Mountains  on  the  west  to  the  Appalachians  on  the 
east,  then  for  the  first  time  became  complete.  The  Mexican 
Gulf  was  much  larger  than  at  present;  but  there  was  not 


218  CENOZOIC   TIME — MAMMALIAN    AGE. 

that  long  extension  far  northward  which  it  had  during  the 
Cretaceous  period.  Florida  was  still  submerged,  and  also 
all  the  bays  of  the  Atlantic  coast  south  of  New  York.  After 
the  Eocene  epoch  the  Mexican  Gulf  became  much  more 
contracted  by  an  elevation  of  the  coast  along  the  Gulf;  and 
by  the  close  of  the  Tertiary  period  the  continent  appears  to 
have  reached  nearly  its  present  outline. 

In  the  Orient  the  Eocene  era  was  one  of  very  extensive 
submergence  of  the  land,  as  shown  by  the  distribution  of 
the  marine  beds  over  Europe,  Asia,  and  northern  Africa, 
as  stated  on  page  208.  After  the  Eocene,  the  greater  part 
of  these  continental  seas  had  become  dry  land,  and  in  gene- 
ral continued  so  afterward;  for  the  Miocene  and  Pliocene  are, 
comparatively,  very  limited  in  extent.  The  fact  that  many 
of  the  great  mountains  of  tb,e  globe,  as  the  Pyrenees,  Alps, 
Carpathians,  Himalayas,  etc.,  were  only  partly  made,  is  here 
proved  by  their  containing  Eocene  rocks  in  their  structure, 
or  by  their  bearing  them  about  their  summits. 

By  evidence  of  this  kind, — the  presence  of  Eocene  strata, 
— it  is  learned  that  the  elevation  of  the  Pyrenees,  though 
commenced  before  the  close  of  the  Cretaceous,  was  mainly 
produced  in  the  middle  or  later  part  of  the  Eocene,  as  also 
that  of  the  Julian  Alps,  the  Apennines  and  Carpathians, 
and  that  of  heights  in  Corsica.  The  elevation  of  the  western 
Alps,  including  Mont  Blanc,  is  referred  by  Elie  de  Beau- 
mont to  the  close  or  latter  part  of  the  Miocene  epoch ;  and 
that  of  the  eastern  Alps,  along  the  Bernese  Oberland,  to 
the  close  of  the  Pliocene.  An  elevation  of  3000  feet  took 
place  in  Sicily  after  the  Pliocene.  The  Himalayas,  in  their 
western  part  about  Cashmere,  have  nummulitic  or  Eocene 
beds,  at  a  height  of  15,000  feet;  so  that  even  this  great  chain, 
although  earlier  elevated  to  the  east,  was  not  completed 
before  the  Middle  Eocene;  and  even  later  than  this,  as  later 
Tertiary  beds  at  lower  levels  show,  it  received  a  consider- 
able part  of  its  elevation. 


POST-TERTIARY   PERIOD.  219 

Many  parts  of  the  region  of  the  Andes  were  raised  3000 
to  500U  feet  or  more  in  the  course  of  the  Tertiary  period. 

Climate. — In  Europe,  the  fact  that  the  plants  of  the  Eocene 
were  Australian  in  character  over  its  central  and  southern 
portions,  and  that  Palms  abounded  in  Britain,  is  evidence 
of  a  tropical  or  sub-tropical  climate  on  the  south,  and  sub- 
tropical or  warm-temperate  on  the  north. 

Again,  the  plants  of  the  Miocene,  in  southern  Europe,  are 
supposed  to  indicate  a  sub-tropical  climate  there  during  the 
middle  Tertiary. 

In  North  America,  the  Eocene  palms  and  other  plants  of 
the  Upper  Missouri  region  show  that  the  temperature  now 
found  in  the  Dismal  Swamp  in  North  Carolina  characterized 
in  the  early  Tertiary  era  the  region  of  the  Upper  Missouri, 
the  vicinity  of  the  Great  Lakes,  and  Yermont  (where  is  the 
Brandon  deposit  of  nuts  and  lignite). 

The  Camels,  Rhinoceroses,  and  other  animals  of  the  Pliocene 
of  the  Upper  Missouri  seem  to  prove  that  a  warm-tem- 
perate climate  still  prevailed  there  in  that  closing  epoch  of 
the  Tertiary  period.  It  is  therefore  plain  that  the  Earth 
had  not  its  present  diversity  of  zones  of  climate ;  and  Europe 
was  apparently  little  if  any  colder  in  the  Eocene  than  in 
the  Jurassic  era.  If  the  interval  between  the  Cretaceous 
and  Tertiary  was  one  of  unusual  cold,  through  Arctic  and 
other  elevations,  as  suggested  on  page  204,  the  cold  epoch 
had  mostly  passed  when  the  Eocene  era  opened. 

II.  POST-TERTIAKY  PERIOD. 

1.  General  characteristics. — The  Post-tertiary  period  was 
remarkable  (1)  as  the  period  of  culmination  of  the  type  of 
Mammals;  and  (2)  as  that  of  high-latitude  movements  and 
operations  both  north  and  south  of  the  equator. 

2.  Epochs. — The  epochs,  as  observed  in  North  America,  are 
two : — 

1.  The  GLACIAL,  or  the  epoch  when,  over  the  higher  lati- 


220  CENOZOIC   TIME — MAMMALIAN    AGE. 

tudes,  the  continents  underwent  great  modifications  in  the 
features  of  the  surface  through  the  agency  of  ice. 

2.  The  CHAMPLAIN,  an  epoch  when  the  ice  had  disap- 
peared, and  the  same  high-latitude  portions  of  the  continent, 
and  to  a  less  extent  the  lower,  became  covered  by  extensive 
fluvial  and  lacustrine  formations,  and  also,  in  some  places, 
by  marine. 

These  epochs  were  followed  in  America  by  another, — the 
TERRACE  epoch, — which  forms  a  transition  to  the  Age  of 
Man;  when  these  fluvial,  lacustrine,  and  marine  formations 
were  made  into  terraced  heights  by  an  elevation  of  the  con- 
tinent which  was  also  in  the  main  a  high-latitude  movement. 

1.  GLACIAL  EPOCH.          \\jecdL-. 

The  special  effects  of  the  operations  going  on  in  the 
Glacial  epoch  are  the  following : — 

1.  Transportation. — The  transportation  of  a  vast  amount 
of  earth  and  stones  from  the  higher  latitudes  to  the  lower, 
over  a  large  part  of  the  breadth  of  a  continent. 

The  material  consists  of  earth  and  pebbles,  or  stones, 
confusedly  mingled  or  unstratified,  and  is  called  drift.  It 
contains  no  marine  fossils  or  relics. 

New  England,  Long  Island,  Canada,  STew  York,  and  the 
States  west  to  Iowa  and  beyond,  are  in  many  parts  thickly 
covered  with  drift;  it  reaches  south  to  the  latitude  of  39°, 
or  nearly  to  the  southern  limits  of  Pennsylvania,  Ohio, 
Indiana,  Illinois,  and  central  Missouri,  being  hardly  trace- 
able south  of  the  Ohio  Eiver. 

The  stones  are  of  all  dimensions,  from  that  of  a  small  pebble 
to  masses  as  large  as  a  moderate-sized  house.  One  at  Brad- 
ford in  Massachusetts  is  30  feet  each  way,  and  its  weight  is 
estimated  to  be  at  least  4,500,000  pounds.  Many  on  Cape 
Cod  are  20  feet  in  diameter.  One  lying  on  a  naked  ledge  at 
"Whitingham  in  Vermont  measures  43  feet  in  length  and  30 
in  height  and  width,  or  40,000  cubic  feet  in  bulk,  and  was 


POST-TERTIARY    PERIOD. 


221 


probably  transported  across  Deerfield  valley,  the  bottom  of 
which  is  500  feet  below  the  spot  where  it  lies. 

The  drift-material  is  coarsest  to  the  north. 

The  directions  in  which  it  travelled  are  in  general  between 
southwestward  and  southeastward,  and  mostly  between 
southward  and  southeastward.  The  material  was  carried 
southward  across  the  great  lakes  and  across  Long  Island 
Sound,  the  land  to  the  south,  in  each  case,  being  covereu 
with  stones  from  the  land  to  the  north. 

The  distance  to  which  the  stones  were  transported,  as 
learned  by  comparing  them  with  the  rocks  in  place  to  the 
north,  is  mostly  between  20  and  40  miles,  though  in  some 
cases  100  miles  or  more. 

2.  Scratches. — The  rocky  ledges  over  which  the  drift  was 
borne  are  often  scratched,  in  closely  crowded  parallel  lines, 
as  in  the  annexed  figure  (fig.  351).  The  scratchings  or  groov- 

Fig.  351. 


Drift  groovings 


ings  are  often  deep  and  broad  channellings,  at  times  even  a 
foot  in  depth  and  several  feet  wide,  as  if  made  by  a  tool  of 
great  size  as  well  as  power.  At  Eowe  in  Massachusetts  and 
on  the  top  of  Mount  Monadnock,  the  scratches  are  of  this 


222  CENOZOIC   TIME — MAMMALIAN   AGE. 

remarkable  character.  These  scratches  occur  wherever  the 
drift  occurs,  provided  the  underlying  rocks  are  sufficiently 
durable  to  have  preserved  them,  and  they  are  usually  of 
great  uniformity  in  any  given  region.  Frequently  two  or 
more  directions  may  be  observed  on  the  same  surface,  as  if 
made  at  different  epochs. 

They  are  found  in  the  valleys  and  on  the  slopes  of  moun- 
tains to  a  height,  on  the  Green  Mountains,  of  5000  feet. 

They  often  cross  slopes  and  valleys  obliquely, — that  is, 
without  following  the  direction  of  the  slope  or  valley.  But, 
when  so,  it  is  usually  found  that  these  valleys  are  tributary 
to  some  great  valley  to  which  the  oblique  scratches  are  more 
or  less  nearly  parallel.  For  the  courses  of  the  scratches 
generally  conform  to  the  directions  of  the  great  valleys  of 
the  land,  rather  than  to  those  of  the  smaller.  Thus,  in  the 
Hudson  River  valley,  between  the  Catskills  and  Green  Moun- 
tains, the  scratches  have  mostly  the  Hudson  River  course ; 
and  in  the  Connecticut  River  valley,  between  the  Green 
Mountains  and  the  heights  of  eastern  Massachusetts,  they 
conform  in  general  to  the  course  of  the  Connecticut  valley. 

While  the  courses  are  generally  from  the  northward  to 
the  southward,  like  those  of  the  drift,  there  are  cases  of 
eastward  and  westward  scratches.  Such  occur  on  the  eleva- 
tions south  of  the  Mohawk  valley,  near  Cherry  Yalley,  and 
over  the  bottom  of  the  Mohawk  valley,  near  Amsterdam, 
at  various  localities ;  they  are  here  parallel  to  the  course  of 
the  great  Mohawk  valley. 

The  stones,  or  boulders,  are  often  scratched  like  the  rocks. 

European  drift. — The  drift  in  Europe  presents  the  same 
general  course  and  peculiarities  as  in  North  America.  It 
reaches  south  to  about  latitude  50°.  The  region  south  of 
the  Baltic,  and  parts  of  Great  Britain,  are  covered  with 
drift  and  stones  from  Scandinavia.  The  distance  of  travel 
varies  from  5  or  10  miles  to  500  or  600. 

3.  Fiords. — Fiords  are  deep  narrow  sea-channels,  running 


POST-TERTIARY   PERIOD.  223 

many  miles  into  the  land.  They  occur  on  the  coasts  of  Nor- 
way, Britain,  Maine,  Nova  Scotia,  Labrador,  Greenland,  on 
the  coast  of  western  North  America  north  of  the  Straits  of 
de  Fuca,  and  that  of  western  South  America  south  of  lati- 
tude 41°  S. 

Fiords  are  thus,  like  the  drift,  confined  to  the  higher  lati- 
tudes of  the  globe;  and  the  two  may  have  been  of  cotempo- 
raneous  origin. 

Origin  of  the  drift. — Nothing  but  moving  ice  could  have 
transported  the  drift  with  its  immense  boulders.  Ice  is  per- 
forming this  very  work  now  in  the  glacier  regions  of  the 
Alps  and  other  icy  mountains,  and  stones  of  as  great  size 
have  in  former  times  been  borne  by  a  slow-moving  glacier 
from  the  vicinity  of  Mont  Blanc  across  the  lowlands  of 
Switzerland  to  the  slopes  of  the  Jura  Mountains,  and  left 
there  at  a  height  of  2203  feet  above  the  present  level  of  Lake 
Geneva.  Moreover,  there  are  scratches,  of  precisely  the 
same  character  as  to  numbers,  depth,  and  parallelism,  in  the 
granitic  and  limestone  rocks  of  the  ridges;  and,  besides, 
the  transported  material  is  left  unstratified,  when  not  after- 
wards acted  upon  and  redistributed  by  Alpine  torrents. 

Icebergs  also  transport  earth  and  stones,  as  in  the  Arctic 
seas;  and  great  numbers  are  annually  floated  south  to  tho 
Newfoundland  banks,  through  the  action  of  the  northern 
or  Labrador  current,  where  they  melt  and  drop  their  great 
boulders  and  burden  of  gravel  and  earth  to  make  unstrati- 
fied deposits.  It  is  objected  to  icebergs  as  the  cause  of  the 
phenomena  of  drift,  that  they  could  not  have  covered  great 
surfaces  so  regularly  with  scratches,  and,  again,  that  there 
are  no  marine  relics  in  the  unstratified  drift  to  prove  that 
the  continent  was  under  the  sea  in  the  Glacial  epoch. 

There  is  a  seeming  difficulty  in  the  Glacier  theory,  from 
the  supposed  want  of  a  sufficient  slope  in  the  surface  to 
produce  movement.  A  slope,  however,  of  one  degree  would 
be  enough.  The  production  of  the  degree  of  cold  required 

20 


224  C2KOZOIC   TIME — MAMMALIAN    AGE. 

to  make  a  glacial  epoch  is  an  indication  that  the  continent 
was  considerably  higher  than  it  is  now  over  its  higher  lati- 
tudes ;  and  the  fiords  are  other  evidence  to  the  same  effect, 
since  they  must  have  been  scooped  out  when  the  land  was 
above  the  sea-level,  so  that  running  water  or  ice  could  have 
carried  on  the  erosion  by  which  they  were  made.  If  a  great 
glacier,  covering  the  land,  had  moved  along  through  its 
extent  but  a  single  mile,  it  would  have  made  scratches  every 
where  beneath  it;  and  50  miles  are  all  that  would  have  been 
required  in  order  to  have  transported  the  boulders  the  dis- 
tances they  are  known  to  have  travelled  in  North  America. 
The  Connecticut  valley  appears  to  have  been  the  course 
of  one  great  independent  glacier;  the  Hudson  valley,  of 
another ;  and  the  Mohawk  valley,  in  the  latter  part  of  the 
epoch  at  least,  of  another. 

2.  CHAMPLAIN  EPOCH. 

The  principal  deposits  of  the  Champlain  epoch  are  of 
three  kinds  : — 

(1.)  Alluvial,  or  those  formed  along  river-valleys  by  the 
action  of  the  streams. 

(2.)  Lacustrine,  or  those  formed  about  lakes. 

(3.)  Sea-border  or  marine,  or  those  formed  on  or  near  sea- 
coasts,  and  often  containing  marine  remains. 

The  alluvial  deposits  occur  in  all  or  nearly  all  the  river- 
valleys  within  the  drift  latitudes  of  the  North  American 
continent,  from  Maine  to  Oregon  and  California;  and  they 
exist  even  farther  south,  in  Kentucky  and  Tennessee,  and 
perhaps  in  the  Gulf  States. 

The  beds  consist  of  earth,  clay,  sand,  or  pebbles,  or  of 
mixtures  of  these  materials.  They  overlie  the  unstratified 
drift  wherever  the  two  are  in  contact. 

They  form  at  present  elevated  alluvial  flats  on  one  or 
both  sides  of  a  river-valley.  Their  elevation  above  the  bot- 
tom of  the  valley  is  greater  in  northern  New  England  than 


POST-TERTIARY   PERIOD.  225 

in  southern  j  and  there  is  a  like  difference  between  those  of 
the  northern  and  southern  parts  of  the  States  to  the  west 
of  New  England. 

The  flats  have  great  extent  along  the  Connecticut  Eiver 
and  its  various  tributaries.     The  view  in  fig.  352  represents 


Terraces  on  the  Connecticut  River,  south  of  Hanover,  N.  H. 

a  scene  a  few  miles  below  Hanover  in  New  Hampshire. 
There  are  here  three  different  levels,  or  terraces,  in  the 


Fig.  353. 


Section  of  a  valley  in  the  Champlain  epoch,  with  dotted  lines  showing  the  terraces  of  the 
Terrace  epoch. 

alluvial  formation ;  the  upper  shows  the  total  thickness  of 
the  formation  down  to  the  river-level. 


226  CENOZOIC   TIME — MAMMALIAN    AGE. 

Figure  353  represents  a  section  of  a  valley,  with  the  allu- 
vial formation,//,  filling  it,  and  the  channel  of  the  river  at 
H.  "Were  the  country  to  be  elevated,  the  river  would  dig 
out  a  deeper  channel  as  the  elevation  went  on,  and  thus  the 
alluvial  formation  would  finally  be  left  far  above  the  river, 
beyond  the  reach  of  its  waters.  The  river  would  at  the 
same  time  wear  away  a  portion  of  the  alluvium  either  side 
during  its  floods,  and  thus  make  room  for  a  lower  flat  on  its 
banks,  over  which  the  flooded  waters  would  spread;  for 
every  river,  not  confined  by  rocks,  has  both  its  channel  and 
its  flood-ground. 

The  lacustrine  deposits  are  of  similar  character,  of  like 
distribution  over  the  continent,  and  in  equally  elevated 
positions  above  the  present  level  of  the  water  they  border. 
The  great  lakes,  as  well  as  the  smaller  lakes  of  the  country, 
are  bordered  by  them. 

The  sea-border  deposits  are  found  along  the  borders  of  the 
sea,  and  often  have  the  character  of  elevated  beaches.  They 
are  found  at  many  places  on  the  coasts  of  New  England, 
both  southern  and  eastern.  At  several  localities  in  Maine 
they  afford  shells  at  heights  not  exceeding  200  feet  above  the 
sea-level.  They  form  deposits  of  great  thickness  along  the 
St.  Lawrence,  as  near  Quebec,  Montreal,  and  Kingston;  at 
Montreal  they  contain  numerous  marine  shells  at  a  height 
of  400  to  500  feet  above  the  river.  They  border  Lake 
Champlain,  being  there  393  feet  in  height  above  its  level; 
and,  besides  marine  shells,  the  remains  of  a  whale  have  been 
taken  from  the  beds. 

In  the  Arctic,  similar  deposits  full  of  shells  are  common, 
at  different  elevations  up  to  600  or  800  feet,  and  in  some 
places  1000  feet,  above  the  sea-level. 

These  sea-border  deposits,  now  elevated,  must  have  been 
at  the  water-level,  or  below  it,  in  the  Champlain  epoch.  The 
facts  prove  that  the  river  St.  Lawrence  was  at  that  time 
an  arm  of  the  sea,  of  great  breadth,  with  the  bordering  land 


POST-TERTIARY   PERIOD.  227 

400  to  500  feet  below  its  present  level;  that  Lake  Champlain 
•was  a  deep  bay  opening  into  the  St.  Lawrence  channel,  and  that 
it  had  its  whales  and  seals  as  well  as  sea-shells ;  that  the  coast 
of  Maine  was  50  to  200  feet  below  its  present  level,  and 
southern  New  England  30  feet  or  more. 

The  present  elevated  positions  of  the  alluvial  and  lacustrine 
formations  over  the  wide  extent  of  the  continent  are  equally 
good  evidence  that  its  mterior,  in  the  Champlain  epoch,  was 
below  its  present  level. 

There  is  thus  proof  that  the  whole  northern  portion  of 
the  continent  was  less  elevated  than  now.  In  fact,  the 
whole  continent  may  have  been  lower;  but,  if  so,  the  northern 
parts  must  have  been  most  depressed,  since  the  sea-border, 
alluvial,  and  lacustrine  formations  are  all  at  higher  elevations 
to  the  north,  or  near  the  northern  boundary  of  the  United 
States,  than  they  are  to  the  south. 

"While,  therefore,  the  facts  connected  with  the  Glacial 
epoch  favor  the  view  that  the  northern  portions  of  the  con- 
tinent were  then  much  raised  above  their  present  level,  those  of 
the  next  or  Champlain  epoch  prove  that  it  was  afterwards 
much  below  its  present  level.  We  hence  learn  that  there  was 
an  upward  high-latitude  movement  for  the  Glacial  epoch, 
and  a  downward  for  the  Champlain  epoch,  and  that  the 
latter  movement  brought  to  its  close  the  epoch  of  ice,  by 
occasioning  a  warm  climate. 

3.  TERRACE  EPOCH. 

"When  the  Champlain  epoch  was  in  progress,  the  upper 
plain  of  the  sea-border  formations,  now  so  elevated,  was  at 
the  sea-level ;  and  the  high  alluvial  plains  along  the  rivers 
were  the  flood-grounds  of  the  rivers.  Since  then  the  land  has 
been  raised ;  and  during  the  progress  of  the  elevation  the 
alluvial  formations  were  cut  into  terraces,  as  represented  in 
fig.  352,  p.  225,  and  the  sea-border  formations,  also,  were  cut 
into  other  terraces,  or  plains,  of  different  levels.  The  epoch 
20* 


228  CENOZOIC    TIME — MAMMALIAN    AGE. 

of  this  elevation  is  hence  called  the  Terrace  epoch.     It  con. 
stitutes  the  transition  to  the  Age  of  Man. 

In  figure  353  there  are  dotted  lines  showing  the  levels  of 
the  river  and  its  flood-plain  at  different  periods  in  this  ele- 
vation ;  and  fig.  354  represents  the  terraces  completed.  The 
successive  terraces  are  not  necessarily  evidence  of  as  ma»y 

Fig.  354. 


Section  of  a  valley  with  its  terraces  completed. 

successive  elevations  of  the  continent,  yet  may  be  so  in 
some  cases. 

As  already  stated,  the  alluvial  formations  throughout  the 
continent,  along  its  various  rivers  and  lakes,  are  raised  high 
above  the  present  flood-plains  of  the  rivers  or  lakes,  and  to 
a  greater  height  in  the  northern  portions  of  the  country 
than  in  the  southern.  Hence,  while  the  Champlain  epoch 
was  one  of  a  low  level  in  the  continent,  especially  at  the 
north,  the  Terrace  epoch  was  one  of  a  rising  again  until 
the  continent  reached  its  present  height;  and  this  rising 
was  greatest  at  the  north. 

The  high-latitude  oscillations  of  this  part  of  geological 
history  were  hence  an  upward  movement  for  the  Glacial 
epoch;  a  downward  for  the  Champlain  epoch;  an  upward 
again  for  the  Terrace  epoch.  There  is  no  evidence  that  the 
movement  resulted  anywhere  in  the  raising  of  a  mountain- 
range  ;  there  was  simply  a  gentle  rising,  then  a  sinking,  and 
then  a  rising  again  of  the  general  surface. 

4.  CHAMPLAIN  AND  TERRACE  EPOCHS  IN  EUROPE. 
There  are  elevated   alluvial,  lacustrine,  and   sea-border 
formations,  of  great  extent,  in  Britain  and  over  the  higher 


POST-TERTIARY    PERIOD.  229 

latitudes  of  Europe,  and  also  other  evidence  that  these 
epochs  were  there  represented  by  phenomena  similar  to 
those  of  America.  But  the  limits  of  the  epochs  have  not 
been  made  out,  and  are  probably  less  clearly  defined.  The 
Glacial  epoch  may  have  been  more  prolonged,  and  the 
grander  northern  oscillations  complicated  by  local  changes 
of  level.  Europe  has  had  its  lofty  glacial  mountains  ever 
since  the  closing  Tertiary  period.  It  u  not  improbable  that 
the  existing  glaciers  of  Norway  and  the  Alps  are  continuations 
of  portions  of  the  more  ancient  glaciers  of  the  continent. 
After  the  Champlain  epoch  there  was  a  time  of  unusual  cold  in 
Europe ;  and  a  glacier  then  covered  all  Switzerland  between 
the  Alps  and  the  Juras  (p.  223) ;  for  the  transported  stones 
and  earth  of  the  glacier  cover  the  alluvial  and  lacustrine 
deposits.  The  simplicity  observed  in  the  order  of  events  in 
American  geological  history  is  not  found  in  any  part  of 
the  European. 

Among  the  British  terraces  those  of  Glen  Eoy  in  Scot- 
land, called  Parallel  roads,  or  Benches,  are  especially  noted. 
There  are  three,  one  above  the  other;  the  highest  1139  feet 
above  tide-level,  the  second  1039  feet,  the  third  847  feet. 
Others  exist  along  many  of  the  rivers  and  about  the  lakes, 
as  well  as  on  the  sea-borders. 

LIFE  OF  THE  POST-TERTIARY. 

The  invertebrate  species  of  the  Post-tertiary,  and  probably 
the  plants,  were  nearly  or  quite  all  identical  with  the  exist- 
ing species.  The  shells  and  other  invertebrate  remains 
found  in  the  beds  on  the  St.  Lawrence,  Lake  Champlain, 
and  the  coast  of  Maine,  are  all  similar  to  those  now  found 
on  the  Labrador  and  Maine  coasts. 

The  life  of  the  period  of  greatest  interest  is  the  Mam- 
malian, which  type,  as  already  remarked,  then  culminated. 
This  culmination  appears  in — (1)  the  number  of  species, 
(2)  the  multitude  of  individuals,  (3)  the  magnitude  of  the 


230  CENOZOIC   TIME — MAMMALIAN   AGE. 

animals, — the  period  in  each  of  these  particulars  exceeding 
the  present  age. 

The  remains  in  America  have  not  been  found  in  the 
unstratified  drift,  but  only  in  the  overlying  Champlain 
deposits,  or  possibly  those  of  more  recent  origin.  In 
Europe  they  are  not  excluded  from  the  drift. 

1.  Europe  and  Asia. — The  bones  of  Mammals  are  found  in 
caves  that  were  their  old  haunts;  in  drift  and  alluvium;  in 
sea-border  deposits ;  in  marshes,  where  the  animals  appear 
to  have  been  mired ;  in  ice,  preserved  from  decay  by  the 
intense  cold. 

The  caves  in  Europe  were  the  resort  especially  of  the 
Great  Cave  Bear  (  Ursus  spelceus),  and  those  of  Britain  of  the 
Cave  Hyena  (Hycena  spelcea~).  Into  their  dens  they  dragged 
the  carcases  or  bones  of  other  animals  for  food,  so  that  relics 
of  a  large  number  of  species  are  now  mingled  together  in 
the  earth,  or  stalagmite,  which  forms  the  floor  of  the  cavern. 
In  a  cave  at  Kirkdale,  England,  portions  of  at  least  75 
Hyenas  have  been  made  out,  besides  remains  of  an  Elephant, 
Tiger,  Bear,  Wolf,  Fox,  Hare,  Weasel,  Rhinoceros,  Horse, 
Hippopotamus,  Ox.  and  Deer,  all  of  which  are  extinct  species. 
A  cave  at  Gaylenreuth  is  said  to  have  afforded  fragments 
of  at  least  800  individuals  of  the  Cave  Bear. 

The  fact  that  the  numbers  of  species  and  of  individuals 
in  the  Post-tertiary  was  greater  than  now,  may  be  inferred 
from  comparing  the  fauna  of  Post-tertiary  Great  Britain 
with  that  of  any  region  of  equal  area  in  the  present  age. 
The  species  included  gigantic  Elephants,  two  species  of 
Rhinoceros,  a  Hippopotamus,  three  species  of  Oxen,  two  of 
them  of  colossal  size,  the  Irish  Elk  (Megaceros  Hibernicus), 
whose  height  to  the  summit  of  its  antlers  was  10  to  11  feet, 
and  the  span  of  whose  antlers  was  8  feet,  or  twice  that  of 
the  American  Moose,  Deer,  Horses,  Soars,  a  Wild-cat,  Lynx, 
Leopard,  a  Tiger  larger  than  that  of  Bengal,  a  large  Lion 
called  a  Machcerodus,  having  sabre-like  canines  sometimes 


POST-TERTIARY   PERIOD.  231 

8  inches  long,  the  Cave  Hyena,  Cave  -Bear,  besides  various 
smaller  species. 

The  Elephant  (Elephas  primigenius)  was  nearly  a  third 
taller  than  the  largest  modern  species.  It  roamed  over 
Britain,  middle  and  northern  Europe,  and  northern  Asia 
even  to  its  Arctic  shores.  Great  quantities  of  tusks  have 
been  exported  from  the  borders  of  the  Arctic  sea  for  ivory. 
These  tusks  sometimes  have  a  length  of  12$  feet.  Near  the 
beginning  of  the  century,  one  of  these  Elephants  was  found 
frozen  in  ice  at  the  mouths  of  the  Lena; -and  it  was  so  well 
preserved  that  Siberian  dogs  ate  of  the  ancient  flesh.  Its 
length  to  the  extremity  of  the  tail  was  16J  feet,  and  its 
height  9J  feet.  It  had  a  coat  of  long  hair.  But  no  amount 
of  hair  would  enable  an  Elephant  now  to  live  in  those 
barren,  icy  regions,  where  the  mean  temperature  in  winter 
is  40°  F.  below  zero. 

Although  there  were  many  Herbivores  among  the  Post- 
tertiary  species  of  the  Orient,  the  most  characteristic  ani- 
mals were  the  great  Carnivores.  The  period  was  the  time 
of  triumph  of  brute  force  and  ferocity,  and  the  Orient — 
and  perhaps  especially  the  part  of  it  in  which  lay  Britain 
and  Europe — was  the  scene  of  its  triumph. 

2.  North  America. — There  were  great  Elephants  and  Mas- 
todons, Oxen,  Horses,  Stags,  Beavers,  and  some  Edentates,  in 
Post-tertiary  North  America,  unsurpassed  in  magnitude  by 
any  in  other  parts  of  the  world.      Herbivores  were  the  cha- 
racteristic type.     Of  Carnivores  there  were  comparatively 
few  species;  no  bone-caverns  have  been  discovered.    Figure 
355  (from  Owen)  represents  the  specimen  of  the  American 
Mastodon  now  in  the  British  Museum.     The  skeleton  set  up 
by  Dr.  Warren  in  Boston   has  a  height  of  11  feet  and  a 
length  to  the  base  of  the  tail  of  17  feet.     It  was  found  in  a 
marsh  near  Newburgh,  New  York.    The  American  Elephant 
was  fully  as  large  as  the  Siberian. 

3.  South  America.— South  America  had  its  Carnivores,  its 


232 


CENOZOIC   TIME — MAMMALIAN   AGE. 


Mastodons,  and  other 'Herbivores ;  but  it  was  most  remark- 
able for  its  Edentates,  or  Sloths,  which  were  wonderful  both 

Fig.  355. 


Skeleton  of  Mastodon  giganteus. 

for  their  magnitude  and  numbers.  Fig.  356  shows  the  form 
and  skeleton  of  one  of  these  animals, — the  Megathere.  It 
exceeded  in  size  the  largest  Rhinoceros :  a  skeleton  in  the 
British  Museum  is  18  feet  long.  It  was  a  clumsy,  sloth-like 
beast,  but  exceeded  immensely  the  modern  sloth  in  its  size. 
Another  kind  of  Edentate  had  a  shell  like  a  turtle,  and  waa 
somewhat  related  to  the  Armadillo.  One  of  them  is  called 
a  Glyptodon  (fig.  357).  The  animals  of  this  kind  were  also 
gigantic,  the  Glyptodon  here  figured  having  had  a  length, 
to  the  extremity  of  the  tail,  of  nine  feet. 

South  America  was  eminently  the  continent  of  Edentates. 


POST-TERTIARY   PERIOD.  233 

4.  Australia. — Post-tertiary  Australia  contained  Marsupial 
animals   almost    exclusively,  like  modern  Australia;   but 

Fig.  356. 


Megatherium  Cuvieri  (X  &). 

these  partook  of  the  gigantic  size  so  characteristic  of  the 
Mammalian  life  of  the  period.  One  species,  called  Dipro- 
todon,  \vas  as  large  as  a  Hippopotamus. 

Conclusions. — The  facts  sustain  the  following  conclusions: 

Fig.  357. 


Glyptodon  clavipes  (X  at)- 

— (1.)  The  Post-tertiary  period  was  the  culminant  time  of 
Mammals,  both  as  to  their  numbers  and  magnitude. 


234  CENOZOIC   TIME. 

(2.)  Each  continent  was  gigantic  in  that  type  of  Mam- 
malian life  which  is  now  eminently  characteristic  of  it :  The 
Orient,  in  Carnivores,  and,  it  may  be  added,  Quadrumanes  or 
Monkeys;  North  America,  in  Herbivores;  South  America,  in 
Edentates;  Australia,  in  Marsupials. 

(3.)  The  climate  of  Great  Britain  and  Europe,  where 
were  the  haunts  of  Lions,  Tigers,  Hippopotamuses,  etc.,  must 
have  been  warmer  than  now,  and  probably  not  colder  than 
warm-temperate.  The  climate  of  Arctic  Siberia  was  such 
that  shrubs  could  have  grown  there  to  feed  the  herds  of 
Elephants,  and  hence  could  not  have  been  below  sub-frigid,  for 
which  degree  of  cold  it  is  possible  the  animals  might  have 
been  adapted  by  their  hairy  covering. 

(4.)  The  meridian  time  of  the  Post-tertiary  Mammals 
was,  hence,  one  of  warmer  climate  over  the  continents  than 
the  present,  and  much  warmer  than  that  of  the  Glacial 
epoch.  The  species  may  have  begun  to  exist  before  the 
Glacial  epoch  ended  in  Europe,  but  belonged  pre-eminently 
to  the  Champlain  epoch,  when  the  lower  level  of  the  land 
over  the  higher  latitudes  would  have  occasioned  a  warm 
climate. 


GENERAL  OBSERVATIONS  ON  THE  CENOZOIC  ERA. 

1.  Contrast  between  the  Tertiary  and  Post-tertiary  periods 
in  geographical  progress. — The  review  of  Cenozoic  time  has 
brought  out  the  true  contrast  in  the  results  of  the  Tertiary 
and  Post-tertiary  periods. 

The  Tertiary  carried  forward  the  work  of  rock-making 
and  of  extending  the  limits  of  dry  land  southward,  south- 
eastward, and  southwestward,  which  had  been  in  progress 
through  the  Cretaceous  period,  and,  indeed,  ever  since  the 
Azoic  age. 

The  Post-tertiary  transferred  the  scene  of  operations  to 
the  broad  surface  of  the  continent,  which  had  been  long 


LIFE.  235 

in  course  of  preparation,  and  especially  to  its  middle  and 
higher  latitudes. 

Through  the  Tertiary  the  higher  mountains  of  the  glohe 
had  been  rising  and  the  continents  extending;  and  hence 
the  great  rivers  with  their  numerous  tributaries — which 

are  the  offspring  of  great  mountains  on  great  continents 

began  to  exist  and  to  channel  out  the  mountains  and  make 
valleys  and  crested  heights.  In  the  Glacial  epoch  this  work 
went  forward  with  special  energy.  The  exposed  rocks  were 
torn  to  fragments  by  the  frosfs  and  moving  ice,  or,  in  regions 
beyond  the  reach  of  glaciers,  by  the  torrents;  the  earth  and 
boulders  formed  were  borne  over  the  surface,  and  the  ex- 
cavation of  valleys  was  everywhere  in  progress.  In  the 
Champlain  epoch,  the  low  level  at  which  the  land  lay,  and 
the  gradual  disappearance  of  the  ice,  enabled  the  flooded 
streams  to  fill  the  great  valleys  deep  with  alluvium.  In  the 
Terrace  epoch,  which  followed,  the  upward  movements  of 
the  land  terraced  the  alluvial  deposits  along  the  river- 
valleys  and  about  the  lakes,  and  completed  the  action  of  the 
rivers  and  vegetation  in  spreading  fertility  over  the  land. 

Thus,  under  the  rending,  eroding,  and  transporting  power 
of  fresh  waters,  frozen  and  unfrozen, — the  great  Post-tertiary 
agent, — in  connection  with  high-latitude  oscillations  of  the 
earth's  crust,  the  surface  of  the  earth  was  brought  into  a 
state  of  preparation  for  the  Age  of  Mind. 

2.  Life. — In  the  Cenozoic  era,  as  in  the  preceding,  exter- 
minations took  place  at  several  successive  times,  and  were 
followed  by  new  creations.  The  Mammals  of  the  early 
Eocene  are  wholly  distinct  from  those  of  the  later;  and 
these  were  distinct  from  any  of  the  Miocene,  the  Miocene 
from  the  Pliocene,  and  the  Post-tertiary  from  the  Pliocene. 

According  to  the  present  state  of  discovery,  Mammals 
commenced  in  the  Mesozoic  era,  late  in  the  Triassic  period, 
and  the  Mesozoic  species  were  all  Marsupials  or  Insectivores. 
They  were  the  precursor  species,  prophetic  of  that  expansion 


236  ERA   OF    MIND. 

of  the  new  type  which  was  to  take  place  after  the  Age  of 
Keptiles  had  closed.  In  the  early  Eocene,  at  the  very  open- 
ing of  the  Age  of  Mammals,  appeared  Herbivores  and  Car- 
nivores of  large  size.  The  Herbivores  were  mostly  Pachy- 
derms, related  to  the  Tapir  and  Hog,  and  distantly  to  the 
Stag.  The  true  Stag-family  among  Euminants,  and  the 
Monkeys,  commenced  in  the  Miocene,  or  possibly  in  the 
later  Eocene;  the  Elephant  tribe,  in  the  Miocene;  the 
Bovine  or  Ox  family,  in  the  Pliocene,  or  late  in  the  Tertiary. 
The  last  group  seems  to  be  mote  than  all  others  especially 
adapted  to  man's  necessities;  and  it  was  accordingly 
among  the  last  of  the  types  introduced  on  the  globe. 


Y.  ERA  OF  MIKD— AGE  OF  MAN. 

With  the  creation  of  Man  a  new  era  in  Geological  history 
opens.  In  earliest  time  only  matter  existed, — dead  matter. 
Then  appeared  life, — unconscious  life  in  the  plant,  conscious 
and  intelligent  life  in  the  animal.  Ages  rolled  by,  with 
varied  exhibitions  of  animal  and  vegetable  life.  Finally 
Man  appeared,  a  being  made  of  matter  and  endowed  with 
life,  but,  more  than  this,  partaking  of  a  spiritual  nature.  The 
systems  of  life  belong  essentially  to  time,  but  Man,  through 
his  spirit,  to  the  opening  and  infinite  future.  Thus  gifted, 
Man  is  the  only  being  capable  of  reaching  towards  a  know- 
ledge of  himself,  of  nature,  or  of  God.  He  is,  hence,  the 
only  being  capable  of  conscious  obedience  or  disobedience 
of  any  moral  law,  the  only  one  subject  to  degradation 
through  excesses  of  appetite  and  violation  of  moral  law,  the 
only  one  with  the  will  and  power  to  make  nature's  forces 
his  means  of  progress. 

Man  shows  his  exalted  nature  in  his  material  structure. 
His  fore-limbs  are  not  made  for  locomotion,  as  in  all 


AGE   OF    MAN.'  237 

quadrupeds.  They  are  removed  from  the  locomotive  to  the 
cephalic  series,  where  they  normally  belong;  for  the  fore-- 
limbs  in  Vertebrates  have  been  shown  to  be  strictly  append- 
ages of  the  occipital  part  of  the"  head,  although  far  displaced 
in  all  excepting  Fishes.  They  are  fitted  to  serve  the  head, 
and  especially  the  intellect  and  soul.  Man  stands  erect,  his 
body  placed  wholly  under  the  brain,  to  which  it  is  sub- 
servient; and  his  feet  are  simply  for  support  and  locomo- 
tion, and  not,  as  in  the  Monkeys,  grasping  or  prehensile 
organs  for  climbing.  His  whole  outer  being,  in  these  and 
other  ways,  shows  forth  the  divine  feature  of  the  inner 
being.  And  nature  acknowledges  with  an  appearance  of 
homage  the  spiritual  element  of  the  new  age ;  for  the  fierce 
tribes  that  attend  Man  have  but  one-fourth  the  size  in  bulk 
of  those  that  possessed  the  earth  in  the  Age  of  Mammals, 
and  all  her  departments  are  full  of  wealth  and  beauty  for 
Man's  good. 

1.  Rock-deposits. 

Stratified  deposits  of  rock-material  are  in  progress  in  the 
Age  of  Man,  as  they  had  been  in  the  preceding  ages.  They 
occur  as  alluvial  beds  along  the  rivers ;  as  lacustrine  in  and 
about  lakes;  as  sea-border  in  beaches,  sand-flats,  shore- 
marshes,  and  off-shore  accumulations  of  earth,  mud,  or  sand; 
and  they  often  contain  buried  shells,  bones,  leaves,— relics 
of  the  living  species  of  the  age.  Elvers,  and,  about  some 
heights,  glaciers,  are  at  work  wearing  down  mountain- 
ridges  and  bearing  the  detritus  to  the  lower  lands.  Ice- 
bergs, laden  with  earth  and  stones,  are  floated  from  the 
Arctic  to  the  banks  of  Newfoundland,  where  they  melt  and 
drop  the  stony  material  over  the  bottom.  Marshes  over 
many  parts  of  the  continents  have  their  accumulations  of 
vegetable  debris  making  peat,  closely  imitating  the  forma- 
tion of  the  great  beds  of  vegetable  debris  of  the  Coal  era. 
The  nature  and  origin  of  these  modern  deposits  are  con- 
sidered  under  Dynamical  Geology. 


238  ERA   OF    MIND. 

The  peculiarity  of  the  age,  as  respects  its  rock-deposits, 
allying  it  to  Cenozoic  time,  and  especially  to  the  Post- 
tertiary,  and  distinguishing  it  from  earlier  ages,  is  the  fact 
that  its  marine  deposits  are  almost  wholly  confined  to  the 
borders  of  the  continents,  the  deposits  of  the  interior  being, 
with  a  few  small  exceptions,  of  terrestrial  or  fresh-water 
origin. 

2.  Life. 

The  Life  of  the  age  has  the  following  among  its  charac- 
teristics : — 

1.  There  is  a  vast  diversity  of  terrestrial  life.    For  the 
continents  have  now  their  greatest  extent  and  their  greatest 
variety  of  climates;  and  hence,  as  life  is  adapted  to  all  its 
different  conditions,  this  life  must  exceed  in  diversity  that  of 
earlier  time,  especially  that  of  all  periods  before  the  Post- 
tertiary.     As   to   Birds  and  Insects,  it  probably  exceeds 
greatly  any  earlier  period  in  number  of  species,  but  not  so  as 
to  Mammals  and  Eeptiles.     In  oceanic  life  the  age  may  be 
far  behind  the  preceding  ages,  both  in  the  number  of  species 
of  most  classes  and  in  the  number  of  individuals  under  the 
species. 

2.  "While  the  Post-tertiary  species  of  Invertebrates  and 
Plants  are  the  same  as  now  exist,  it  cannot  be  asserted  that 
all  now  living  then  existed.    It  is  probable  that,  as  the  Post- 
tertiary  period  drew  to  its  close,  and  the  present  climates 
of  the  globe  were   introduced   by  the   movements  of  the 
earth's  crust  in  the  following  Terrace  epoch  (p.  228),  there 
were  large  additions  of  species,  especially  of  those  adapted 
to  promote  Man's  physical,  intellectual,  and  moral  progress, 
through  their  nutritious  or  healing  virtues,  their  strength 
and  beauty,  and  their  power  of  multiplying  the  necessities 
of  labor  and  the  evils  of  indolence. 

3.  The  peculiar  Mammalian  life  of  the  age  appears  to 
have  commenced  its  existence  mostly  in  the  Terrace  epoch, 
as  is  proved  by  the  fact  that  their  remains  are  found  in 


AGE    OF    MAN.  239 

ancient  alluvium  in  the  same  latitudes  of  Europe  in  which 
they  now  occur,  or  even  in  lower  latitudes.  For  this  shows 
that  the  species  were  distributed  over  the  continent  very 
much  as  they  are  now,  and  therefore  that  the  climate  of 
Europe  was  essentially  the  same  as  now;  and  this  was  true 
as  the  Terrace  epoch  made  progress,  and  not  before  it  in 
the  Champlain  epoch  (p.  234). 

4.  The  Mammals  of  the  age  have  not  more  than  one-fourth 
the  bulk  of  those  of  the  Post-tertiary,  the  Elephants,  Lions, 
Tigers,  Elk,  Deer,  Horses,  Sloths,  Kangaroos,  Beavers,  etc., 
being  all  of  much  reduced  size. 

5.  When  the  Mammals  of  the  age  first  appeared,  there 
were  still   some  of  the   great   Post-tertiary   Mammals   in 
existence, — as  the  Elephant,  Rhinoceros,  Cave-Sear ,  and  some 
others, — as  is  proved  by  the  bones  of  these  species  occurring 
in  the  same  beds  with  those  of  modern  animals. 

The  cooling  climate  of  the  progressing  Terrace  epoch 
may  have  occasioned  the  final  extermination  of  the  giant 
Post-tertiary  animals. 

6.  Man,  the  dominant  species  of  the  age,  adds  a  new  class 
of  fossils  to  the  earth's  deposits.     There  are,  besides  his 
own    bones,  remains  of  his   works,  as,  for   example,  flint 
arrow-heads   and   hatchets,  carved   wood,  coins,  books    or 
parchments,  buried  cities  like  Pompeii  and  Nineveh. 

Figure  358  represents  a  fossil  skeleton  of  Man  from  a 
shell-rock  of  Guadaloupe.  It  is  the  remains  of  an  Indian 
killed  in  battle  two  centuries  since;  and  the  rock  is  of  the 
same  kind  with  that  which  is  now  forming  and  consolidating 
on  the  shores.  Figure  359  represents  a  coin-conglomerate 
containing  silver  coins  of  the  reign  of  Edward  I.,  found 
at  a  depth  of  ten  feet  below  the  bed  of  the  river  Dove  in 
England. 

7.  Man  appears  to  have  begun  his  existence  in  the  Terrace 
epoch,  before  the  complete  extinction  of  the  Post-tertiary 
Mammals;    for  flint  arrow-heads   and  some  other  human 


240 


ERA    OF    MIND. 


relics  are  found  in  deposits  and  caverns  containing  bones  of 
the  same  Post-tertiary  species  that  are  mentioned  in  §  5,  as 
near  Abbeville  and  Amiens  in  France,  and  at  a  few  other 
localities  in  Europe  and  in  Britain. 

8.  Man  is  of  one  species.  He  stands  alone  at  the  summit 
of  the  system  of  life. 

He  was  created  in  the  temperate  zone, — for  the  species 
degenerates  in  the  tropics ;  and  in  the  warmer  part  of  the 

Figs.  358,  359. 


Conglomerate  containing  coins. 


temperate,  because  this  would  best  suit  his  primitive  con- 
dition, without  arts  or  education. 

His  place  of  origin  was  not  on  both  the  Occidental  and 
Oriental  continents;  for  no  species  of  Mammals  (excepting 
some  in  the  Arctic)  are  common  to  the  two;  but  in  the 
Orient,  which  was  the  continent  of  the  highest  of  Mammals 
through  the  Age  of  Mammals,  and  which  thereby  promised 
to  take  the  lead  in  future  progress.  No  place  of  origin 
better  accords  with  the  conditions  requisite  for  the  species  in 


AGE   OF    MAN.  241 

its  original  state  and  for  the  commencement  of  its  develop- 
ment than  that  region  in  western  Asia,  which  is  a  central 
point  of  radiation  for  the  three  great  Oriental  lands,  Asia, 
Europe,  and  Africa,  where  the  Bible  places  his  creation. 

9.  Some  species  of  animals  have  become  extinct  since  the 
Age  of  Man  began,  and  through  Man's  agency.  The  Dodo, 
a  large  bird  looking  like  an  overgrown  chicken  in  its  plum- 
age and  wings,  was  abundant  in  the  island  of  Mauritius 
until  early  in  the  commencement  of  the  eighteenth  century. 
The  Hoa,  or  Dinornis,  is  a  New  Zealand  bird  of  the  Ostrich 
kind  that  was  living  less  than  a  century  since ;  it  was  10  or 
12  feet  in  height,  and  the  tibia  ("  drumstick")  30  to  32  inches 
long.  In  Madagascar  remains  of  a  still  larger  bird,  but  of 
similar  character,  occur,  called  an  ^Epiornis;  its  egg  is  over 
a  foot  (13 £  inches)  long.  These  are  a  few  of  the  examples  of 
the  modern  extinction  of  species. 

The  progress  of  civilization  tends  to  restrict  forests  and 
forest-life  to  narrower  and  narrower  limits.  The  Buffalo 
once  roamed  over  North  America  to  the  Atlantic,  but  now 
lives  only  on  the  Eocky  Mountain  slopes  west  of  the  Mis- 
souri Eiver.  The  Beaver  formerly  ranged  over  the  United 
States  from  the  Pacific  to  the  Atlantic,  as  well  as  to  the 
Arctic,  and  many  of  their  remains  occur  in  caverns  near 
Carlisle  in  Pennsylvania.  It  is  now  rarely  seen  east  of 
the  Missouri  Eiver,  though  occasionally  met  with  in 
northern  New  York  and  in  some  parts  of  the  Appalachians 
to  the  southwest.  The  beaver,  wolf,  bear,  and  wild-boar 
were  formerly  common  in  Britain,  but  are  now  wholly 
exterminated. 

3.  Changes  of  Level 

The  earth  in  this  Age  of  Man — its  ages  of  progress  past — 
has  beyond  question  reached  an  era  of  comparative  repose. 
Its  rocks  are  essentially  completed ;  its  mountains  are  made ; 
its  great  outlines,  early  defined,  have  been  filled  out  with 


242  ERA   OP   MIND. 

their  various  details;  and,  now  that  the  system  of  life  is 
finished  in  the  last  creation,  Man,  the  Earth,  Man's  resi- 
dence, is  also  in  its  finished  state.  But  yet  not  only  is  the 
formation  of  rocks  still  in  progress, — the  forces  of  nature 
continuing  to  work  as  in  former  ages, — but  there  are  also 
changes  of  level  going  on  of  the  same  kind  with  those  of 
past  time. 

These  changes  of  level  are  either  paroxysmal, — that  is,  take 
place  through  a  sudden  movement  of  the  earth's  crust  as 
sometimes  happens  in  connection  with  an  earthquake;  or 
they  are  secular, — that  is,  result  from  a  gradual  movement 
prolonged  through  many  years  or  centuries.  The  following 
are  some  examples  : — 

1.  Paroxysmal. — In   1822,  the    coast  of   western    South 
America  for  1200  miles  along  by  Concepcion  and  Valpa- 
raiso was  shaken  by  an  earthquake,  and  it  has  been  esti- 
mated that  the  coast  near  Valparaiso  was  raised  at  the 
time  3  or  4  feet.     In  1835,  during  another  earthquake  in 
the  same  region,  there  was  an  elevation,  it  is  stated,  of  4  or 
5  feet  at  Talcahuano,  which  was  reduced  after  a  while  to  2 
or  3  feet.    In  1819  there  was  an  earthquake  about  the  Delta 
of  the  Indus,  and  simultaneously  an  area  of  2000  square 
miles,  in  which  the  fort  and  village  of  Sindree  were  situated, 
sunk  so  as  to  become  an  inland  sea,  with  the  tops  of  the 
houses  just  out  of  water;  and  another  region  parallel  with 
the  sunken  area,  50  miles  long  and  in  some  parts  10  broad, 
was  raised  10  feet  above  the  delta.     These  few  examples  all 
happened  within  an  interval  of  sixteen  years.     They  show 
that  the  earth  is  still  far  from  absolute  quiet,  even  in  this  its 
finished  state. 

2.  Secular. — Along  the  coasts  of  Sweden  and  Finland  on 
the  Baltic  there  is  evidence  that  a  gradual  rising  of  the  land 
is  in  slow  progress.     Marks  placed  along  the  rocks  by  the 
Swedish   government,  many   years    since,    show   that   the 
change  is  slight  at  Stockholm,  but  increases  northward,  and 


GEOLOGICAL   TIME.  243 

is  felt  even  at  the  North  Cape,  1000  miles  from  Stockholm. 
At  Uddevalla  the  rate  of  elevation  is  equivalent  to  3  or  4 
feet  in  a  century. 

In  Greenland,  for  6DO  miles  from  Disco  Bay,  near  69°  N., 
to  the  firth  of  Igaliko  60°  43'  N.,  a  slow  sinking  has  been 
going  on  for  at  least  four  centuries.  Islands  along  the  coast, 
and  old  buildings,  have  been  submerged.  The  Moravian 
settlers  have  had  to  put  down  new  poles  for  their  boats,  and 
the  old  ones  stand  "  as  silent  witnesses  of  the  change." 

It  is  suspected  that  a  sinking  is  also  in  progress  along  the 
coast  of  New  Jersey,  Long  Island,  and  Martha's  Vineyard, 
and  a  rising  in  different  parts  of  the  coast-region  between 
Labrador  and  the  Bay  of  Fundy.  There  are  deeply  buried 
stumps  of  forest-trees  along  the  seashore  plains  of  New 
Jersey,  whose  condition  can  hardly  be  otherwise  explained. 

The  above  cases  illustrate  movements  by  the  century,  or 
those  slow  oscillations  which  have  taken  place  through  the 
geological  ages,  raising  and  sinking  the  continents,  or  at 
least  changing  the  water-line  along  the  land. 

This  fact  is  to  be  noted,  that  these  secular  movements  of 
the  Age  of  Man  are,  so  far  as  observed,  high-latitude  oscilla- 
tions, just  as  they  were  in  the  Post-tertiary  period;  and  they 
indicate,  therefore,  that  the  Post-tertiary  system  of  changes 
has  not  yet  reached  its  final  end. 


GENERAL  OBSERVATIONS  ON  GEOLOGICAL 
HISTORY. 

1.  LENGTH  OF  GEOLOGICAL  TIME. 

By  employing  as  data  the  relative  thickness  of  the  form- 
ations of  the  Geological  ages,  estimates  have  been  made  of 
the  time-ratios  of  those  ages,  or  their  relative  lengths  (pp. 
145,  198).  These  estimated  time-ratios  for  the  Paleozoic, 


244  HISTORICAL   GEOLOGY. 

Mesozoic,  and  Ccnozoic  arc  14  : 4  :  3,  equivalent  to  3}  :  1 :  f  j 
— that  is,  Paleozoic  time  was  3£  times  as  long  as  the  Meso- 
zoic, and  the  Cenozoic  \vas  three-fourths  as  long.  But  the 
numbers  may  be  much  altered  when  the  facts  on  which 
they  are  based  arc  more  correctly  ascertained.  There  is  no 
doubt  that  the  Paleozoic  era  exceeded  the  Mesozoic  in  length 
3  or  4  times,  and  probably  was  full  twice  as  long  as  the  Meso- 
zoic and  Cenozoic  united.  It  is  also  quite  certain  that  the 
first  of  the  Paleozoic  ages — the  Silurian — was  at  the  least 
three  times  as  long  as  either  the  Devonian  or  Carbonif- 
erous. 

Hence  comes  the  striking  conclusion  that  the  longest  age 
of  the  world  since  life  began  was  the  earliest, — when  the 
earth  was  even  without  fishes  and  numbered  in  its  popula- 
tion only  Radiates,  Mollusks,  and  marine  Articulates.  And 
the  time  of  the  earth's  beginnings  before  the  introduction 
of  lifo  may  have  exceeded  in  length  all  subsequent  time. 

The  actual  lengths  of  these  ages  it  is  not  possible  to  deter- 
mine even  approximately.  All  that  Geology  can  claim  to 
do  is  to  prove  the  general  proposition  that  Time  is  long. 

One  of  the  means  of  calculation  which  have  been  appealed 
to  is  that  afforded  by  the  Falls  of  Niagara.  The  river 
below  the  Falls  flows  northward  in  a  deep  gorge,  with  high 
rocky  walls,  for  seven  miles,  towards  Lake  Ontario.  It  is 
reasonably  assumed  that  the  gorge  has  been  cut  out  by  the 
river,  for  the  river  is  annually  making  progress  of  this  very 
kind.  From  certain  fossiliferous  Post-tertiary  beds  over  the 
country  bordering  the  present  walls,  it  is  proved  that  the 
present  gorge,  about  six  miles  long,  was  not  made  before 
the  Glacial  epoch.  The  present  annual  progress  of  the 
gorge  from  the  cutting  and  undermining  action  of  the 
waters  has  been  variously  estimated  from  three  feet  a  century 
to  one  foot  a  year.  At  the  larger  estimate  of  one  foot  a  year, 
the  six  miles  would  have  required  31,000  years;  and  if  the 
estimate  be  one  inch  a  year,  or  8i  feet  a  century,  the  timo 


GEOGRAPHICAL  PROGRESS.  245 

becomes  nearly  380.000  years.  Since  one  foot  a  year  :s 
proved  by  observation  to  be  altogether  too  large  an  esti- 
mate, the  calculation  may  be  regarded  as  at  least  esta- 
blishing the  proposition  that  Time  is  long,  although  it  affords 
no  satisfactory  numbers. 

Other  modes  of  calculation  fully  establish  this  general 
proposition.  Some  estimates  which  have  been  recently 
made  seem  to  show  that  it  is  true  even  of  the  Age  of  Man; 
but  they  are  based  on  too  imperfect  a  knowledge  of  facts  to 
be  of  value. 

2.  GEOGRAPHICAL  PROGRESS  IN  NORTH  AMERICA. 

The  principal  steps  of  progress  in  the  continent  of  North 
America  are  here  recapitulated  : — 

1.  The  continent  at  the  close  of  the  Azoic  lay  spread  out 
mostly  beneath  the  ocean  (map,  p.  73).     Although  thus  sub- 
merged, its  outline  was  nearly  the  same  as  now.  The  dryland 
lay  mostly  to  the  north,  as  shown  in  the  map.     The  form 
of  the  main  mass  approximated  to  that  of  the  letter  V,  and 
it  had  a  southeast  and  a  southwest  border  nearly  parallel  to 
its  present  outline. 

2.  Through  the  Paleozoic  ages,  as  the  successive  periods 
passed,  the  dry  land  gradually  extended  itself  southward  in 
consequence  of  a  gradual  elevation  ;  that  is,  the  sea-border 
at  the  close  of  the  Lower  Silurian  was  as  far  south  as  the 
Mohawk  valley  in  New  York ;  at  the  close  of  the  Upper 
Silurian  it  extended  along  not  far  from  the  north  end  of 
Cayuga  Lake  and  Lake  Erie;  and  by  the  close  of  the  Devo- 
nian'age  the  State  was  a  portion  of  the  dry  land  nearly  to 
its  southern  boundary.    This  progress  southward  of  the  sea- 
border  in  New  York  may  be  taken  as  an  example  of  what 
occurred  along  the  borders  of  the  Azoic  to  the  westward. 
In  other  words,  there  was  through  the  Silurian  and  Devo- 
nian ages  a  gradual  southerly  extension  of  the  dry  part  of 
the  continent, — that  is,  to  the  southeastward  and  the  south- 
westward. 


246  HISTORICAL   GEOLOGY. 

By  the  close  of  the  Carboniferous  age,  or  before  the  open- 
ing of  the  Mesozoic  era,  the  dry  portion  appears  to  have  so 
far  extended  southwardly  as  to  include  nearly  all  the  area 
east  of  the  Mississippi  and  north  of  the  Gulf  States,  along 
with  a  part  of  that  west  of  the  Mississippi,  as  far  nearly  as 
the  western  boundary  of  Kansas. 

3.  Before  the  Silurian  age  began,  and  in  its  first  period, 
great  subsidences  were  in  progress  along  the  Lake  Superior 
region,  when  the  thick  Huronian  and  Potsdam  formations 
were  made.    The  facts  show  that  the  depression  of  the  lake, 
and  probably  that  of  some  of  the  other  great  lakes,  and 
also  that  of  the  river  St.  Lawrence,  began  to  form  either 
during  the  closing  part  of  the  Azoic  age  or  in  the  early 
part  of  the  Silurian  age. 

4.  During  the   Paleozoic  ages,  rock-formations  were  in 
progress  over  large  parts  of  the  submerged  portions  of  the 
continent  up  to  the  sea-borders,  and  some  vast  accumula- 
tions of  sand  were  made  as  drifts  or  dunes  over  the  flat 
shores  and  reefs.    These  rock-formations  had  in  general  ten 
times  the  thickness  along  the  Appalachian  region  which 
they  had  over  the  interior  of  the  continent ;  and  they  were 
mostly  fragmental  deposits  in  the  former  region,  while  mostly 
limestones  in  the  latter.     Hence  two  important  conclusions 
follow  :— 

First.  The  Appalachian  region  was  through  much  of  the 
time  an  exposed  shore-reef  or  flat  of  great  extent,  parallel 
in  course  with  the  present  sea-border  as  well  as  that  of  the 
ancient  Azoic;  while  the  interior  was  a  shallow  sea  opening 
southward  freely  into  the  Gulf  of  Mexico,  and  only  during 
some  few  of  the  periods  with  the  same  freedom  eastward 
directly  into  the  Atlantic.  Most  of  the  western  part  of  the 
sea  (west  of  Missouri)  appears  to  have  been  too  deep  for  de- 
posits between  the  Lower  Silurian  and  Carboniferous  eras. 

Secondly.  The  Appalachian  region  was  undergoing, 
through  the  Silurian  and  Devonian  ages,  great  changes  of 


GEOGRAPHICAL  PROGRESS.  247 

level,  and  the  amount  of  subsidence  involved  exceeded  by 
ten  times  tbat  in  the  Interior  Continental  region. 

5.  Of  this  Appalachian  region,  some  or  all  of  the  Green 
Mountain  portion  was  elevated  above  the  ocean's  level  at 
the  close'  of  the  Lower  Silurian ;  and  at  the  same  time  the 
valley  of  Lake  Champlain  and  Hudson  Eiver  was  formed 
or  began. 

This  valley  and  the  depressions  of  the  Great  Lakes,  and 
also  those  of  the  lakes  extending  in  a  line  through  British 
America  northwestward  from  Lake  Superior  to  the  Arctic, 
lie  not  far  from  the  borders  of  the  Azoic  continent,  and, 
therefore,  between  the  portion  of  the  continent  that  was 
comparatively  stable  dry  land  from  the  time  of  the  Azoic 
onward,  and  that  portion  which  was  receiving  rock-forma- 
tions and  undergoing  oscillations  of  level.  To  this  they 
owe  their  origin. 

6.  As  the  Paleozoic  era  closed,  an  epoch  of  revolution 
occurred,  in  which  the  rocks  of  the  Appalachian  region  and 
those  of  the  Eastern  border  underwent — (1)  great  changes  of 
level;  (2)  extensive  flexures  or  foldings;  (3)  immense  fault- 
ings  in  some  parts ;  (4)  consolidation,  and,  in  the  eastern 
half  especially,  crystallization  or  metamorphism  on  a  grand 
scale,  and  the  loss  of  bitumen  by  the  coal-beds  changing 
them  into  anthracite.      These  changes  affected  the  region 
from  Labrador  to  Alabama.     The  effects  of  heat  and  uplift 
were  more  decided  toward  the  Atlantic  than  toward  the 
interior,  showing  that  the  force  producing  the  great  results 
was   exerted  in  a  direction  from  the  Atlantic  inland,  or 
from    the   southeast   toward   the   northwest.      The  Appa- 
lachian Mountains  were  then  made;  and  they  were,  con- 
sequently, in  existence  when  the  Mesozoic  era  opened. 

These  mountains  are  parallel  to  the  eastern  outline  of  the 
original  Azoic  continent.  The  outline  of  the  New  York 
Azoic  peninsula  is  repeated  in  the  trend  of  the  Appalachian 
chain  along  through  western  New  England  and  Pennsyl- 

22 


248  HISTORICAL   GEOLOGY. 

vania  (the  direction  in  New  England  being  nearly  north  and 
south  and  in  Pennsylvania  as  nearly  east  and  west),  and  it 
is  again  repeated  in  the  eastern  and  southern  coasts  of  New 
England. 

Similar  changes  may  have  taken  place  on  the  Pacific  side; 
but  facts  proving  this  have  not  yet  been  collected. 

The  epoch  of  revolution  was  equally  revolutionary  in 
Europe.  No  living  species  are  known  to  have  survived  from 
the  Paleozoic  into  the  Mesozoic. 

7.  In  the  early  or  middle  Mesozoic  period  (the  continent 
being  largely  dry  land,  as  stated  in  the  latter  part  of  §  2), 
long  depressions  in  the  surface  of  the  continent,  made  in  the 
course  of  the  Appalachian  revolution  and  situated  between 
the  Appalachians  and  the  sea-border,  were  brackish-water 
estuaries,  or   were   occupied  by  fresh-water  marshes   and 
streams ;  and  Mesozoic  sandstone,  shale,  and  coal-beds  were 
formed  in  them.    The  Connecticut  valley  region  of  Mesozoic 
rocks  (p.  164)  is  one  example.    At  the  same  time  there  were 
formations  in  progress  over  the  Rocky  Mountain  region,  a 
vast  area  from  which  the  sea  was  not  excluded,  or  only 
in  part :  the  shores  of  this  Mesozoic  interior  sea  appear  to 
have  extended  through  Kansas  near  the  meridian  of  20° 
west  of  Washington  (97°  west  of  Greenwich). 

8.  In  the  later  Mesozoic,  or  the  Cretaceous  period,  the 
continent  had  its  Atlantic  and  Gulf  border  yet  under  water, 
and  Cretaceous  rocks  were  formed  about  them,  and  thus  the 
continent  continued  its  former  course  of  enlargement  south- 
eastward (see  map,  p.  196).     The  Western  Interior  sea,  open- 
ing south  into   the  Gulf  of  Mexico,  just  alluded  to,  still 
existed,  and  deposits  were  made  in  it  over  a  very  large  part 
of  the  great  region  reaching  from  Kansas  on  the  east  to  the 
Colorado  on  the  west.     The  Pacific  border  was  also  receiv- 
ing an  extension  like  the  Atlantic. 

9.  In  the  early  Cenozoic,  or  Tertiary  period,  the  exten- 
sion of  the  Atlantic  and  Pacific  borders  was  still  continued. 


GEOGRAPHICAL   PROGRESS.  249 

With  its  close  the  progress  of  the  continent  in  rock-making 
southeastward  and  southwestward  was  very  nearly  com- 
pleted. 

The  Western  Interior  sea  had  become  greatly  contracted 
after  the  Cretaceous  period  by  the  elevation  of  the  Eocky 
Mountain  region;  and,  although  the  Mexican  Gulf  still 
remained  of  more  than  twice  its  present  area,  it  was  much 
reduced  in  size  (map,  p.  217).  At  the  beginning  of  the 
Tertiary  period  the  Ohio  and  Mississippi  reached  an  arm  of 
the  Gulf  just  where  they  join  their  waters;  at  its  close  the 
Ohio  had  taken  a  secondary  place  as  a  tributary  of  the 
Mississippi.  The  great  Missouri  Eiver,  the  real  trunk  of 
the  Interior  river-system  rather  than  the  Mississippi,  began 
its  existence  after  the  Cretaceous  period,  and  reached  its 
full  size  only  towards  the  close  of  the  Tertiary,  when  the 
Eocky  Mountains  had  finally  attained  their  full  height. 

10.  The  elevation  of  the  Eocky  Mountains,  like   that  of 
the  Appalachians,  was  the  raising  of  the  land  along  a  region 
parallel  with  the  outline  of  the  original  Azoic  continent 
(see  map,  p.  73).      The  elevation  of  the  Cascade  range  of 
Oregon  and  Sierra  Nevada  of  California  was  a  doubling  of 
this  same  line  on  the  west;  while  the  elevation  of  the  trap 
ridges  and  red  sandstone  of  the  early  Mesozoic  along  the 
Atlantic  border  (p.  165)  was  a  doubling  of  the  line  on  the 
east. 

11.  The  continent  being  thus  far  completed,  as  the  Post- 
tertiary  period  was  drawing  on,  operations  changed  from 
those  causing  southern  extension  to  those  producing  move- 
ments of  ice  and  fresh  waters  over  the  land,  especially  in 
the  higher  latitudes;  and  thereby  valleys,  great  and  small, 
were  excavated  over  the  continent;  earth  and  gravel  were 
transported  and  made  to  cover  deeply  the  rocks  and  spread 
the  continent  with  fertile  plains  and  hills;  and,  as  the  final 
result,  those  grand  features  and  those  qualities  of  surface 


250  HISTORICAL   GEOLOGY. 

were  educed  that  were  requisite  to  make  the  sphere  a  fit 
residence  for  Man. 

"Y  /t I  A,  3.  PROGRESS  OF  LIFE.  _ 

From  the  survey  of  the  Life  of  the  globe  which  has  been 
made,  the  following  conclusions  may  be  drawn.  Future 
discovery  may  change  some  of  the  details;  but  it  is  not 
probable  that  it  will  affect  the  general  principles  announced. 

1.  Fact  of  progress  of  life. — Life  commenced  among  plants 
in  Sea-weeds;  and  it  ended  in  Palms,  Oaks,  Elms,  the  Orange, 
Rose,  etc.     It  commenced  among  animals  in  Lingulce  (Mol- 
lusks standing  on  a  stem  like  a  plant)  and  in  Crinoids  and 
Trilobites,  if  not  earlier  in  the  simple  systemless  Protozoans 
(p.  58) ;   it    ended  in  Man.      Sea-weeds  were  followed  by 
Ferns  and   other  Flowerless  plants,    and  by  Gymnosperms, 
the  lowest  of  Flowering  plants ;    these  finally  by  the  higher 
Flowering  species  above  mentioned, — the  Palms  and  Angio- 
sperms.     Radiates,  Mollusks,  and  Articulates  of  the  Silurian 
afterwards  had  Fishes  associated  with  them;  later,  Reptiles; 
later,  Birds  and  inferior  Mammals;  later,  higher  Mammals,  as 
Beasts  of  prey  and  Cattle;  lastly,  Man. 

2.  Progress  from  marine  to  terrestrial   life. — The  Silurian 
and  Devonian  were  eminently  the  marine  ages  of  the  world. 
The  plants  of  the  Silurian  arc  sea-weeds,  and  the  animals  all 
marine.     The  animals  of  the  Devonian,  also,  are  mainly 
marine;  but  there  is  a  step  taken  in  terrestrial  life  by  the 
introduction  of  land-plants  and  Insects. 

In  the  Carboniferous  age  and  through  the  Mesozoic  era 
the  continents,  or  large  areas  over  them,  underwent  alter- 
nations between  a  submerged  state  and  dry  land,  leading  a 
kind  of  amphibian  existence.  The  Carboniferous  age  had, 
besides  aquatic  life  and  Insects,  its  terrestrial  Mollusks  and 
Centipedes,  its  Amphibian  and  other  Eeptiles,  besides  a 
great  profusion  of  forest-trees  and  other  terrestrial  vegeta- 


PROGRESS   OF   LIFE.  251 

tion.     In  the  early  Mesozoic,  to  Eeptiles  were  added  Birds 
and  Mammals,  eminently  terrestrial  kinds  of  life. 

The  Ceuozoic  was  distinctively  a  continental  era.  The 
continents  became  mostly  dry  land  after  its  earliest  epoch; 
and  as  the  Age  of  Man  approached,  they  had  their  full  size 
and  their  present  diversities  of  surface  and  climate.  With 
the  increased  variety  of  conditions  fitted  for  terrestrial  life 
there  was,  beyond  question,  a  great  augmentation  in  the 
number  and  variety  of  terrestrial  species.  Mammals  were 
most  numerous  in  kinds  in  the  Post-tertiary;  but  Birds  and 
Insects  have  probably  their  greatest  numbers  and  variety 
of  species  in  the  present  age.  Marine  species  still  abound, 
but  relatively  to  the  terrestrial  they  are  far  less  numerous 
and  less  extensively  distributed  than  in  the  Mesozoic  and 
earlier  ages. 

3.  Progress  was  connected  with  a  constant  change  of  life  by 
exterminations  and  the  introduction  of  new  species. — No  species 
of  animal  survived  from  the  beginning  of  life  on  the  globe 
to  the  present  time,  nor  even  through  a  single  one  of  the 
several  geological  ages;  and  but  few  lived  on  from  the 
beginning  of  any  one  of  the  many  periods  to  its  close,  or 
from  one  period  to  another. 

There  were  universal  exterminations,  according  to  the 
existing  state  of  testimony  (with  perhaps  an  exception  as 
regards  some  species  of  oceanic  life,  p.  203),  closing  some  of 
the  ages,  as  the  Carboniferous  and  the  Eeptilian;  there  were 
exterminations,  nearly  as  complete,  closing  the  periods  on 
each  of  the  continents;  and  others,  usually  less  complete, 
closing  epochs ;  and  often  some  exterminations  accompany- 
ing each  change  in  the  rock-depositions  that  were  in  pro- 
gress. For,  in  passing  from  one  bed  to  another  above,  some 
fossils  fail  that  occur  below;  and  from  the  strata  of  one 
epoch  to  another,  still  larger  proportions  disappear;  and 
sometimes  with  the  transitions  to  rocks  of  another  period 
or  age,  all  the  species  are  different. 
22* 


252  HISTORICAL   GEOLOGY. 

Of  all  genera  of  animals  now  having  living  species,  only 
two  (and  those  Molluscan,  Lingula  and  Distinct)  commenced 
their  existence  in  the  earliest  Silurian ;  every  other  genus 
of  that  early  time  sooner  or  later  numbered  only  extinct 
species. 

Such  unbroken  lines  prove  the  oneness  of  plan  or  system 
through  geological  history,  and,  therefore,  of  purpose  in  the 
Creator. 

Five  hundred  species  of  Trilobite  lived  in  the  course  of 
the  Paleozoic  ages :  afterward  there  were  none.  900 
species  of  the  Ammonite  group  existed  in  the  Mesozoic, 
— not  all  at  once,  but,  as  in  the  case  of  the  Trilobites,  in  a 
succession  of  genera  and  species :  the  last  then  disappeared. 
There  have  been  450  species  of  the  Nautilus  tribe  in  exist- 
ence :  now  there  are  but  2  or  3,  and  these  are  peculiar  to 
the  present  age.  700  species  of  Ganoids  have  been  found 
fossil :  the  tribe  is  now  nearly  extinct.  The  remains  of 
2500  species  of  plants  and  nearly  40,000  species  of  animals 
have  been  found  in  the  rocks,  not  one  of  which  is  now  in 
existence.  These  are  a  few  examples  of  the  extinctions  of 
tribes  that  have  taken  place.  But  the  number  of  kinds  of 
fossils  discovered  cannot  be  the  number  of  species  that 
have  existed ;  and  the  above  numbers  of  marine  species 
may  safely  be  multiplied  by  three,  and  of  terrestrial  by 
twenty. 

The  facts  show  that  the  life  of  the  world  underwent  con- 
stant changes  through  exterminations  and  creations. 

4.  Progress  not  always  begun  by  the  introduction  first  of  the 
lowest  species  of  a  group. — Mosses,  although  inferior  to  Ferns, 
appear  to  have  been  of  later  introduction,  for  no  remains 
have  been  found  in  the  Carboniferous  or  Devonian  rocks, 
in  which  rocks  there  are  relics  of  both  Ferns  and  Gymno- 
sperms. 

The  earliest  of  Fishes,  instead  of  being  those  of  lowest 
grade,  were  among  the  highest :  they  were  Ganoids,  or  rep- 


PROGRESS    OF    LIFE.  253 

tilian  Fishes  (that  is,  a  kind  intermediate  in  some  respects 
between  Fishes  and  Reptiles),  along  with  others  of  the 
order  of  Selachians  or  Sharks,  the  superior  division  of  the 
class.  Trilobites  of  the  first  fauna  of  the  Silurian  are  not 
the  lowest  of  Crustaceans.  No  fossil  Snakes  have  been 
found  below  the  Cenozoic,  although  large  Eeptiles  abounded 
in  the  Mesozoic.  Oxen  date  from  the  later  Tertiary,  long 
after  the  first  appearance  of  many  higher  Mammals,  as 
Tigers,  Dogs,  Monkeys,  etc. 

There  was  upward  progress  in  the  grand  series  of  species, 
as  stated  in  §  1,  but  there  was  not  progress  in  all  cases  from 
the  lowest  species  to  the  highest. 

5.  The  earliest  species  of  a  group  were  often  those  of  a  com- 
prehensive type. — The  Ganoid  fishes  are  an  example  of 
these  comprehensive  types.  As  stated  on  page  111,  they 
were  intermediate  between  Fishes  and  Eeptiles;  they  were 
fishes  comprehending  in  their  structure  some  Eeptilian  cha- 
racters, and  hence  called  comprehensive  types. 

The  Selachians  are  another  example  of  a  comprehensive 
type ;  for  the  sharks  have  some  important  peculiarities  in 
which  they  approximate  to  the  higher  Vertebrates  and  even 
Mammals,  as  is  seen  in  their  mode  of  development  and  in 
the  very  small  number  of  their  young. 

Fishes  commenced  with  these  two  comprehensive  types, 
— the  Ganoid  and  Selachian. 

The  earliest  Mammals  were  Marsupials,  or  species  of 
Mammals  comprehending  in  their  structure  some  character- 
istics of  oviparous  Mammals  (see  p.  50),  and,  therefore,  in 
certain  respects  intermediate  between  Mammals  and  Ovipa- 
rous Vertebrates. 

The  vegetation  of  the  coal  era  included  trees  allied  to  the 
small  Ground-pine  or  Lycopodia  of  the  present  day;  and 
these,  as  well  as  the  Lycopodia,  constitute  a  type  interme- 
diate in  some  points  between  Ferns  and  Pines  or  Conifers 
(p  108).  There  were  at  the  same  time  Sigillariae, — a  typo 


254  HISTORICAL   GEOLOGY. 

allied  closely  to  the  Pine  tribe,  but  intermediate  between  it 
and  the  Lycopodia  and  Ferns. 

In  the  Mesozoic  the  most  characteristic  plants  were 
Cycads;  and  these  comprehended  in  their  structure  some- 
thing of  three  distinct  types.  They  are  most  closely  like 
Conifers  in  fruit;  but  they  are  like  Ferns  in  tbe  way  the 
leaves  unfold,  and  in  some  other  points,  and  like  Palms  in 
their  habit  of  growth  and  their  foliage  (p.  167). 

These  comprehensive  types  embraced  in  their  natures 
usually  the  features  of  some  type  that  was  to  appear  in  the 
future.  Thus,  the  Ganoid  fishes  of  the  Devonian  in  a  sense 
foreshadowed  the  type  of  Reptiles,  the  species  under  which 
did  not  come  into  existence  until  long  afterward  in  the 
Carboniferous  age.  The  Cycads  in  a  similar  manner  fore- 
shadowed the  Palms,  a  type  which  did  not  appear  until  the 
Cretaceous  period. 

6.  Harmony  in  the  life  of  a  period  or  age. — Through  the 
existence  of  these  comprehensive  types,  and  also  in  other 
ways,  there  was  always  a  striking  degree  of  harmony 
between  the  species  making  up  the  population — or  the 
fauna  and  flora — of  each  period  in  the  world's  history. 

Among  the  plants  of  the  Carboniferous  age  there  were — 
(1)  the  highest  of  the  Cryptogams,  or  Flowerless  plants,  the 
Ferns;  (2)  the  lowest  of  Phenogams  (Gymnosperms),  or 
Flowering  plants,  species  having  only  inconspicuous  and 
imperfect  flowers,  and  hence  almost  flowerless ;  and  (3)  the 
intermediate  types  of  Lycopodia  (Lepidodendra)  and  Sigil- 
Iaria3. 

Again,  in  the  Mesozoic  the  terrestrial  Vertebrate  life 
included— (1)  Reptiles,  which  are  oviparous  species;  (2) 
Birds,  also  oviparous  species ;  (3)  reptilian  Birds,  having  long 
tails  like  the  Reptiles,  a  comprehensive  type;  (4)  Insect- 
ivorous (Insect-eating)  Mammals;  (5)  st.ni-oviparous  Mam- 
mals, or  Marsupials,  an  intermediate  type  between  the  true 
Insectivores  and  the  oviparous  Reptiles  and  Birds. 


PROGRESS   OF   LIFE.  255 

This  kind  of  harmony  existed  in  all  the  ages. 

It  exists  none  the  less  now  when  the  types  have  their 
widest  diversity;  for  the  less  size  of  the  brute  beasts 
than  in  the  Post-tertiary,  remarked  upon  on  page  239,  and 
the  reference  throughout  the  Flora  and  Fauna  of  the  world 
to  Man,  arc  in  full  harmony  with  the  spiritual  being  at 
the  head  of  the  existing  creation. 

7.  Progress  always  the  gradual  unfolding  of  a  system — Man 
the  culmination  of  that  system. — There  were  higher  and  lower 
upccies  created  through  all  the  ages,  but  the  successive 
populations  were  still,  in  their  general  range,  of  higher  and 
higher  grade ;  and  thus  the  progress  was  ever  upward.  The 
type  or  plan  of  vegetation,  and  the  four  grand  types  or 
plans  of  animal  life  (the  Eadiate,  Molluscan,  Articulate, 
and  Vertebrate),  ordained  in  the  act  of  creation,  were  each 
displayed  under  multitudes  of  tribes  and  species,  rising  in 
rank  with  the  progress  of  time,  and  all  under  relations  so 
harmonious  and  so  systematic  in  their  successions  that  they 
seem  like  the  expression — in  material  living  forms — of  one 
divine  idea. 

With  every  new  fauna  and  flora  in  the  passing  periods, 
there  was  a  fuller  and  higher  exhibition  of  the  kingdoms 
of  life.  Had  progress  ceased  with  the  Post-tertiary,  when 
the  world  was  given  up  to  brute  passion  and  ferocity,  the 
system  might  have  been  pronounced  the  scheme  of  an  evil 
demon.  But,  as  time  moved  on,  Man  came  forth, — not  in 
strength  of  body,  but  in  the  majesty  of  his  spirit;  and  then 
living  nature  was  full  of  beneficence.  The  system  of  life, 
about  to  disappear  as  a  thing  of  the  past,  had  its  final  pur- 
pose fulfilled  in  the  creation  of  a  spiritual  being, — one  hav- 
ing powers  to  search  into  the  depths  of  nature  and  use  the 
wealth  of  the  world  for  his  physical,  intellectual,  and  moral 
advancement,  that  he  might  thereby  prepare,  under  divine 
aid,  for  the  new  life  in  the  coming  future. 

Thus,  through  the  creation  of  Man  completing  the  system 


256  HISTORICAL   GEOLOGY. 

of  life,  all  parts  of  that  system  became  mutually  consistent 
and  full  of  meaning,  and  Time  was  made  to  exhibit  its  true 
relation  to  Eternity. 

Methods  of  exterminations  of  species  and  extinctions  of  tribes. 
— (1.)  Some  species  of  plants  and  animals  require  dry  land 
for  their  support  and  growth ;  some,  fresh-water  marshes  or 
lakes;  some,  brackish  water;  some,  seashore  or  shallow 
marine  waters;  some,  deeper  ocean-waters. 

Hence,  (a)  movements  in  the  earth's  crust  submerging 
large  continental  areas,  or  raising  them  from  the  condition 
of  a  sea-bottom  to  dry  land,  would  exterminate  life : — sink- 
ing them  in  the  ocean,  extinguishing  terrestrial  life,  raising 
them  from  the  ocean,  extinguishing  marine  life.  In  early 
times,  when  the  continental  surface  was  in  general  nearly 
flat,  a  change  of  level  of  a  few  hundred  feet,  or  perhaps  of 
even  100,  would  have  been  sufficient  for  a  wide  extermi- 
nation. If  a  modern  coral  island  were  to  be  raised  150  feet, 
its  reef-forming  corals  would  all  be  killed;  or  if  sunk  in  the 
ocean  150  feet,  the  same  result  would  follow, — because  the 
species  do  not  grow  below  a  depth  of  100  feet.  And  if  all 
the  coral-reefs  of  the  Pacific  were  simultaneously  sunk  or 
raised  to  the  extent  stated,  there  would  be  a  total  extinction 
of  a  large  number  of  species. 

(6)  Along  a  seacoast  the  bays  and  inlets  sometimes 
are  closed  by  barriers  thrown  up  by  the  sea,  and  hence 
become  fresh,  killing  all  marine  life.  Again,  barriers  are 
often  washed  away  by  the  sea,  and  then  salt  water  enters, 
destroying  fresh-water  life. 

(2.)  Species  are  also  made  for  a  limited  range  of  tempera- 
tures: some,  for  the  equatorial  regions  only;  some,  for  the 
cooler  part  of  the  tropical  zone;  some,  for  the  warmer 
temperate  latitudes;  some,  for  the  middle  temperate; 
some,  for  the  colder  temperate ;  some,  for  the  frigid  zone ; 
and  few  species  live  through  two  such  zones. 


PROGRESS   OF   LIFE.  257 

Hence,  (a)  as  the  earth  has  gradually  cooled  in  its 
climates  from  a  time  of  universal  tropics  to  that  of  the 
present  condition,  those  tribes  or  families  made  for  the 
earlier  condition  of  the  globe  afterward  became  of  necessity 
extinct.  This  may  be  a  reason  why  many  of  the  tribes  of 
the  ancient  world  disappeared,  and  why  the  Keptilian  type 
culminated  in  the  Mesozoic;  these  species  were  made  espe- 
cially for  the  warm  condition  which  then  prevailed. 

Again,  (6)  any  temporary  change  of  climate  over  the 
globe — from  cold  to  warm  or  warm  to  cold — would  have 
exterminated  species.  An  increase  in  the  extent  and  height 
of  Arctic  lands  would  have  increased  the  cold,  as  shown  by 
Lyell,  and  thereby  sent  cold  winds  south  over  the  conti- 
nents and  cold  oceanic  currents  south  along  the  border  of 
the  oceans. 

On  the  contrary,  a  diminution  in  the  extent  of  Arctic 
lands,  making  the  higher  regions  open  seas,  or  an  increase 
in  the  extent  of  tropical  lands  for  the  sun  to  heat,  would 
have  increased  the  heat  of  the  globe  and  sent  a  warm 
climate  far  north. 

Such  changes  are  destructive  to  living  species.  It  is  sug- 
gested on  p.  204  that  the  destruction  of  life  at  the  close  of 
the  Mesozoic  may  have  arisen  from  the  cause  here  explained. 

(3.)  The  heat  which  has  escaped  from  the  earth's  interior 
through  the  crust,  in  connection  with  igneous  eruptions,  or 
seasons  of  metamorphic  changes  when  the  earth's  rocks 
were  crystallizing  on  a  vast  scale,  would  have  caused  a 
destruction  of  all  marine  life  in  the  vicinity;  and  where 
metamorphic  action  has  taken  place  through  an  area  a  thou- 
sand miles  or  more  in  length,  as  in  the  progress  of  the 
Appalachian  revolution  (p.  155),  the  devastation  must  have 
extended  over  a  large  part  of  the  continental  area. 

Origination  of  species. — Geology  affords  no  support  to  the 
hypothesis  that  species  have  been  made  from  pre-existing 


258  HISTORICAL   GEOLOGY. 

species,  and  suggests  no  theory  of  development  by  natural 
causes.  In  other  words,  it  has  no  facts  sustaining  the  notion 
that  Man  was  made  through  the  gradual  progress  or  im- 
provement of  some  one  of  the  Apes,  or  by  any  method  of 
development  out  of  an  Ape,  or  that  Elephants  were  so  made 
from  Mastodons,  or  the  reverse,  or  from  any  other  species, 
or  one  species  of  Monkey,  Cat,  Horse,  etc.,  from  another;  and 
much  less  does  it  favor  the  hypothesis  that  the  whole  sys- 
tem of  animal  life  is  nothing  but  a  growth  from  one,  two, 
or  more  original  species,  one  changing  into,  or  evolving, 
another,  through  a  method  of  development,  as  supposed  in 
a  development-hypothesis.  The  facts  the  science  has  thus 
far  collected  prove  that  a  system  of  life  has  been  gradually 
brought  out  in  the  course  of  the  ages.  But  it  gives  no 
information,  in  the  author's  opinion,  as  to  the  manner  in 
•which  the  Divine  will  called  into  existence  the  successive 
tribes  or  species. 

The  science  in  its  present  state  affords  the  following  evi- 
dence bearing  on  this  subject: — 

1.  Species  do  not  shade  into  one  another  as  if  they  had 
originated  by  transitions  from  one  another.     For  example, 
the  Post-tertiary  Mastodon  and  Elephant  of  North  America 
do  not  pass  into  one  another  or  into  other  earlier  species; 
or  the  Apes  into  the  species  Man  ;  or  any  Mollusks  or  Articu- 
lates, through  a  series  of  stages,  into  Fishes;  or  any  Sea- 
weeds into  Ferns  or  the  earliest  land-plants,  etc.      The  spe- 
cies of  plants  and  animals  at  the  present  day  as  well  as 
those  of  the  past,  with  comparatively  few  exceptions,  have 
their  limits  well  denned,  and  do  not  blend  with  one  another 
by  insensible  gradations. 

2.  Groups  commence  sometimes  in  their  higher  species. 
Thus,  Fishes — the  earliest  of  Vertebrates — began  with  the 
Ganoids  and  Sharks,  with  no  evidence  of  a  progress  upward 
from  lower  species.    The  first  of  Land-plants  are  the  Ferns, 


PROGRESS   OP   LIFE.  259 

Lepidodendra,  etc.  ;  and  no  species  of  the  inferior  group  of 
Mosses  have  been  found  marking  a  line  of  progress  upward 
to  the  Lepidodendra.  Many  other  such  cases  might  be  men- 
tioned. 

3.  The  earth's  progress  has  involved  the  occurrence  at 
intervals  of  revolutions  or  devastations.  Some  of  these 
devastations  appear  to  have  been  nearly  or  quite  universal 
over  the  globe,  while  others  have  been  confined  to  single 
continents,  or  limited  areas,  and  have  been  only  partial  (see 
p.  162).  But,  whether  universal  or  not,  they  have  often  cut 
off  short  not  only  species,  but  genera,  families,  and  tribes;  and 
yet  the  same  genera,  families,  and  tribes  have  had  new 
species  afterwards.  Life  has  been  re-introduced  where  it 
had  been  exterminated,  as  if  the  system  were  not  at  the 
mercy  of  temporary  catastrophes,  but  owed  its  restoration 
and  continued  progress  to  a  power  that  was  independent  of 
all  causes  of  desolation  and  could  even  use  desolation  as  a 
means  of  progress. 

The  advocates  of  a  development-hypothesis  do  not  deny 
the  above  evidence;  but  they  argue  that  the  records  are 
very  imperfect,  full  of  long  breaks;  and,  again,  that  only  a 
small  part  of  the  world  has  been  searched  for  its  truths,  and 
that  part  not  thoroughly. 

But  a  hypothesis  unsustained  by  facts  just  where  it  would 
be  most  natural  to  look  for  them,  and  resting  for  its  geolo- 
gical basis  on  possible  discoveries  in  the  future,  may  well  be 
left  to  pass  as  a  mere  suggestion  until  the  discoveries  have 
been  made.  This  is  the  dictate  of  true  Science. 

Geology  has  no  theory  of  creation  to  present;  and  its 
discoveries  are  already  so  extensive,  and  so  corroborative  of 
the  general  results  arrived  at,  from  whatever  continent  they 
have  been  gathered,  that  its  present  silence  is  in  weighty 
opposition  to  such  views.  The  science  testifies  to  the  fact 
that  plants  and  animals  have  come  into  existence  in  a  long 

23 


260  HISTORICAL   GEOLOGY. 

succession  of  species.  It  demonstrates  the  oneness  in  plan 
and  purpose  of  all  nature,  and  thereby  the  oneness  of  its 
Author.  It  points  to  boundless  wisdom  in  every  step  of 
progress,  and  with  increasing  distinctness  as  the  era  ap- 
proaches when  Man  should  appear  and  receive  the  Divine 
command,  "  Subdue  and  have  dominion."  But  it  directs 
to  no  cause  of  the  origin  of  species  but  the  Cause  of  causes, 
— the  infinite  God. 

In  the  account  of  creation  given  in  the  first  chapter  of 
Genesis,  it  is  stated  that  on  the  fifth  day  the  waters  brought 
forth  abundantly  the  moving  creature  that  hath  life,  the 
flying  creatures  of  the  air,  and  the  great  whales  (a  word 
meaning  as  truly  reptiles).  In  the  commencing  Silurian 
the  first  appearance  of  the  swarming  life  of  the  waters  took 
place  (p.  93).  In  the  Devonian,  Fishes  and  Insects  were 
added;  in  the  Carboniferous,  Reptile  life  began;  and  in  the 
Mesozoic,  Birds  as  well  as  Reptiles  existed,  and  the  latter 
became  the  dominant  life  of  the  globe.  At  the  same  time, 
small  semi-oviparous  Manimals,  or  Marsupials,  with  probably 
some  Insectivores,  appeared  as  precursors  of  the  age  that 
w&s  next  to  follow.  "With  the  close  of  the  Mesozoic  the 
Reptile  world  ended  j  and  so  ended  also  the  fifth  day  of  the 
Mosaic  record. 

On  the  sixth  day  there  were  two  great  works, — first,  the 
creation  of  Mammals,  and,  as  a  second,  the  creation  of  Man. 

"With  the  opening  Cenozoic,  Mammals  came  forth  in 
great  numbers  and  of  large  size ;  and  as  the  era  advanced, 
they  increased  in  variety  until  the  type  reached  an  expan- 
sion as  to  magnitude  of  individuals  and  numbers  of  kinds 
even  exceeding  the  exhibition  of  it  in  the  present  age. 
Thus  passed  the  first  portion  of  the  sixth  day.  Finally 
Man  appeared  as  the  last  great  work. 

Creation  finished,  the  day  of  rest  followed, — the  era  of 


PROGRESS    OF   LIFE.  261 

the  finished  world,  the  era  also  of  Man's  prog  ress  and  pre- 
paration for  another  and  a  higher  life.  Ana  as  the  "  six 
days"  work  of  creation  is  succeeded  by  a  seventh  of  rest, 
so,  it  has  been  well  said,  the  Sabbath  closes  man's  week,  as 
a  day  of  rest  and  of  preparation  for  that  spiritual  life. 


PART  IV. 

DYNAMICAL  GEOLOGY. 


DYNAMICAL  GEOLOGY  treats  of  the  causes  or  origin  of 
events  in  Geological  history, — that  is,  of  the  origin  of  rocks, 
— of  disturbances  of  the  earth's  strata,  and  their  eifects, 
— of  valleys, — of  mountains, — of  continents, — and  of  the 
changes  in  the  earth's  features,  climates,  and  living  species. 

The  agencies  of  most  importance,  next  to  the  universal 
power  of  Gravitation,  are  Life,  the  Atmosphere,  Water,  Heat, 
and  Cohesive  and  Chemical  attraction. 

The  following  are  the  subdivisions  of  the  subject  here 
adopted: — 1.  Life;  2.  The  Atmosphere;  3.  Water;  4.  Heat 
— the  mechanical  eifects  of  the  Atmosphere,  "Water,  .and 
Heat  being  considered  under  these  heads ;  5.  Movements  in 
the  earth's  crust,  and  their  consequences,  including  the  fold- 
ing and  uplifting  of  strata,  the  production  of  earthquakes, 
and  the  origin  of  mountains  and  of  the  earth's  general 
features.  Chemical  Geology,  which  treats  of  the  chemical 
operations  connected  with  the  origin  of  rocks,  constitutes 
another  division  of  the  subject,  but  is  not  here  taken  up. 

I.  LIFE. 

Life  has  done  much  geological  work  by  contributing  mate' 
rial  for  the  making  of  rocks.  Nearly  all  the  limestones  of 

262 


PEAT-FORMATIONS.  263 

the  globe,  all  the  coal,  and  some  siliceous  beds,  besides  por- 
tions of  rocks  of  other  kinds,  have  been  formed  out  of  the 
stony  relics  of  living  species. 

Through  simple  growth  and  the  power  of  secretion,  Ver- 
tebrates form  a  bony  skeleton ;  Mollusks  make  shells,  which 
are  calcareous,  or  nearly  of  the  composition  of  common 
limestone;  Polyps  make  Corals,  also  calcareous;  Crinoids 
make  stems  and  flower-like  skeletons  that  are  calcareous ; 
and  the  Polyps  and  Crinoids,  although  as  really  animal  as 
any  quadruped,  are  yet  so  low  in  organization  that  nine- 
tenths  of  the  bulk  of  the  animal  are  often  stony  (calca- 
reous), and  still  the  functions  of  life  are  perfectly  carried  on. 

There  are  various  kinds,  also,  of  microscopic  species 
which  contribute  to  the  material  of  rocks.  The  Bhizopods 
among  animals  (p.  59)  make  calcareous  shells,  each  con- 
taining one  or  many  minute  cells;  the  Diatoms  among 
microscopic  plants  (p.  61)  make  siliceous  shells ;  the  Poly- 
cystines  among  microscopic  animals  make  siliceous  shells. 

Plants  also  make  beds  of  coal  and  peat  out  of  accumula- 
tions of  leaves  and  stems,  as  already  in  part  explained  on 
page  135. 

In  further  illustration  of  this  subject,  three  examples  of 
rock-making  may  be  described: — 1.  Peat-formations;  2. 
Beds  of  microscopic  organisms ;  3.  Coral-reefs. 


1.  Peat-formations. 

Peat  is  an  accumulation  of  half-decomposed  vegetable 
matter  formed  in  wet  or  swampy  places.  In  temperate 
climates  it  is  due  mainly  to  the  growth  of  mosses  of  the 
genus  Sphagnum.  These  mosses  form  a  loose  turf;  and,  as 
they  have  the  property  of  dying  at  the  extremities  of  the 
roots  while  increasing  above,  they  may  gradually  form  a  bed 


23* 


264  DYNAMICAL   GEOLOGY. 

of  great  thickness.  The  roots  and  leaves  of  other  plants, 
or  their  branches  and  stumps,  and  any  other  vegetation 
present,  may  contribute  to  the  accumulating  bed.  The  car- 
casses and  excrements  of  dead  animals  at  times  become 
included.  Dust  may  also  be  blown  over  the  marsh  by  the 
winds. 

In  wet  parts  of  Alpine  regions  there  are  various  flowering 
plants  which  grow  in  the  form  of  a  close  turf,  and  give  rise 
to  beds  of  peat  like  the  moss.  In  Fuegia,  although  not 
south  of  the  parallel  of  56°,  there  are  large  marshes  of  such 
Alpine  plants,  the  mean  temperature  being  about  40°  F. 

The  dead  and  wet  vegetable  mass  slowly  undergoes  a 
change,  becoming  an  imperfect  coal,  of  a  brownish-black 
color,  loose  in  texture,  and  often  friable,  although  com- 
monly penetrated  with  rootlets.  In  the  change  the  woody 
fibre  loses  a  part  of  its  gases ;  but,  unlike  coal,  it  still  con- 
tains usually  25  to  33  per  cent,  of  oxygen.  Occasionally  it 
is  nearly  a  true  coal. 

Peat-beds  cover  large  surfaces  of  some  countries,  and 
occasionally  have  a  thickness  of  forty  feet.  One-tenth  of 
Ireland  is  covered  by  them;  and  one  of  the  "mosses"  of  the 
Shannon  is  stated  to  be  fifty  miles  long  and  two  or  three 
broad.  A  marsh  near  the  mouth  of  the  Loire  is  described 
by  Blavier  as  more  than  fifty  leagues  in  circumference. 
Over  many  parts  of  New  England  and  other  portions  of 
North  America  there  are  extensive  beds.  The  amount  in 
Massachusetts  alone  has  been  estimated  to  exceed  120,000,000 
of  cords.  Many  of  the  marshes  were  originally  ponds  or 
shallow-  lakes,  and  gradually  became  swamps  as  the  water, 
from  some  cause,  diminished  in  depth.  The  peat  is  often 
underlaid  by  a  bed  of  whitish  shell  marl,  consisting  of  fresh- 
water shells — mostly  species  of  Cyclas  and  Planorbis  — 
which  were  living  in  the  lake.  There  are  often  also  beds 
of  the  siliceous  shields  of  Diatoms. 

Peat  is  used  for  fuel  and  also  as  a  fertilizer.     When  pre- 


BEDS    OF    MICROSCOPIC   ORGANISMS.  265 

pared  for  burning,  it  is  cut  into  large  blocks  and  dried  in 
the  sun.  It  is  sometimes  pressed  in  order  to  serve  as  fuel 
for  steam-engines.  Muck  is  another  name  of  peat,  and  is 
used  especially  when  the  material  is  employed  as  a  manure; 
but  it  includes  also  impure  varieties  not  fit  for  burning, 
being  applied  to  any  black  swamp-earth  consisting  largely 
of  decomposed  vegetable  matter. 

Peat-beds  sometimes  contain  standing  trees,  and  entire 
skeletons  of  animals  that  had  sunk  in  the  swamp.  The 
peat-waters  have  often  an  antiseptic  power,  and  flesh  is 
sometimes  changed  by  the  burial  into  adipocere. 


2.  Beds  of  Microscopic  Organisms. 

Microscopic  life  abounds  in  almost  all  waters,  especially 
over  muddy  bottoms, — as  in  lakes,  rivers,  marshes,  salt- 
water swamps,  harbors,  bays,  the  shallow  borders  of  the 
ocean,  and  also  the  deep  ocean.  Part  of  the  species  make 
no  stony  secretions,  but  much  the  larger  part  form  calca- 
reous or  siliceous  shells.  Although  these  shells  are,  with 
few  exceptions,  exceedingly  minute,  the  most  part  wholly 
invisible  unless  highly  magnified,  thty  are  in  so  vast  num- 
bers in  many  places,  and  multiply  so  rapidly,  that  they  form 
in  time  thick  beds  out  of  their  accumulated  shells.  A  square 
yard  covered  with  these  microscopic  species  will  increase 
upward  not  only  as  fast  as  a  square  yard  of  an  oyster-bank, 
but  much  more  rapidly,  because  of  their  extreme  simplicity 
of  structure,  their  rapid  reproduction,  and  the  fact  that 
nearly  the  whole  bulk  of  each  one  is  in  stony  material. 

The  calcareous  species,  or  Rhizopods,  abound  in  the  shal- 
lower waters  along  the  borders  of  the  ocean,  and  also  over  its 
bottom  where  thousands  of  feet  deep.  Over  what  is  called 
the  Telegraphic  plateau,  between  Ireland  and  Newfoundland, 
they  appear  to  make  a  nearly  continuous  bed  for  a  thousand 


266  DYNAMICAL   GEOLOGY. 

miles  or  more  in  breadth,  and  perhaps  more  than  this  from 
north  to  south.  The  thickness  of  the  great  limestone- 
formation  there  in  progress,  out  of  these  minute  shells,  is 
of  course  unknown.  The  genera  of  shallow  water  are 
mostly  different  from  those  of  the  deep  sea. 

The  siliceous  species  are  either  Diatoms  or  Polycystines. 
They  occur  both  in  shallow  and  deep  waters,  like  the  Rhizo- 
pods.  The  Diatoms  are  found  in  cold  as  well  as  warm  seas, 
and  in  fresh  waters  as  well  as  marine.  Over  the  bottoms  of 
shallow  lakes  they  make  thick  beds,  just  as  the  Rhizopods 
do  in  the  ocean;  and  many  of  the  peat-beds  rest  on  a  thick 
layer  of  Diatoms  made  from  species  that  were  living  in  the 
lake  that  afterwards  became  the  peat-growing  swamp. 

The  rock  made  of  Rhizopod  shells  is  exemplified  in  chalk, 
— a  soft  white  or  whitish  limestone.  That  consisting  of 
Diatoms  often  looks  like  a  very  fine  whitish  earth ;  but  it  is 
sometimes  compacted  into  a  nearly  solid  mass,  and  some- 
times into  an  imperfect  slate. 

On  p.  192  it  is  stated  that  the  flint  which  occurs  in  chalk 
may  have  been  made  from  the  silica  of  Diatoms  and  of  the 
spicula  of  sponges. 

These  are  examples  of  beds  formed  by  simple  growth  and 
multiplication  of  living  species.  The  shells  are  in  size  like 
the  grains  of  a  fine  powder;  and  it  is  only  necessary  that 
they  be  consolidated  as  they  lie,  in  order  that  a  compact 
rock  shall  be  made  out  of  the  accumulation. 

3.  Coral-Keefs. 

In  tropical  regions  corals  grow  in  vast  plantations  about 
most  oceanic  islands  and  the  shores  of  the  continents. 
The  greatest  depth  at  which  the  reef-making  species  live 
is  about  100  feet;  and  from  this  depth  to  sometimes  a  foot 
above  low-tide  level,  they  flourish  well.  The  patches  or 
groves  of  coral  are  usually  distributed  among  larger  areas 


CORAL-REEFS.  267 

of  coral  sand,  like  small  groves  of  trees  or  shrubbery  in 
some  sandy  plains. 

The  corals  have  much  resemblance  to  vegetation  in  their 
forms  and  their  modes  of  growth;  and  the  animals  are 
so  like  flowers  in  shape  and  bright  colors  that  they  are 
called  flower-animals  (p.  57).  Along  with  the  corals  there 
are  also  .great  numbers  of  Shells,  besides  Crabs,  Echini,  and 
other  kinds  of  marine  life. 

The  coral  plantations  are  swept  by  the  waves,  and  with 
great  force  when  the  seas  are  driven  by  storms.  The  corals 
are  thus  frequently  broken,  and  the  fragments  washed  about 
until  they  are  either  worn  to  ^and  by  the  friction  of  piece 
upon  piece,  or  become  buried  in  the  holes  among  the  growing 
corals,  or  are  washed  up  the  beach.  Corals  are  not  injured 
by  mere  breaking,  any  more  than  is  vegetation  by  the  clip- 
ping of  a  branch,  and  those  that  are  not  torn  up  from  the 
very  base  and  reduced  to  fragments  continue  to  grow. 

The  fragments  and  sand  made  by  the  waves,  and  by  the 
same  means  strewed  over  the  bottom  along  with  the  shells 
also  of  Mollusks,  commence  the  formation  of  a  bed  of  coral- 
rock, — literally  a  bed  of  limestone,  for  the  coral  and  shells 
have  the  composition  of  limestone.  As  the  corals  continue 
growing  over  this  bed,  fragments  and  sand  are  constantly 
forming,  and  the  bed  of  limestone  thus  increases  in  thick- 
ness. In  this  manner  it  goes  on  increasing  until  it  reaches 
the  level  of  low  tide ;  beyond  this  it  rises  but  little,  because 
corals  cannot  grow  wholly  out  of  water,  and  the  waves  have 
too  great  force  at  this  level  to  allow  of  their  holding  their 
places,  if  they  were  able  to  stand  the  hot  and  drying  sun. 
The  bed  of  calcareous  rock  thus  produced  is  a  coral-reef. 

Since  reef-corals  grow  to  a  depth  of  only  100  feet,  the 
thickness  of  the  reef  cannot  much  exceed  100  feet  if  the 
sea-bottom  remains  at  a  constant  level,  except  where  there 
are  oceanic  currents  to  transport  to  greater  depths  the  sant1 
that  is  made.  But  should  the  reef-region  be  slowly  sink 


268  DYNAMICAL   GEOLOGY. 

ing  at  a  rate  not  faster  than  the  corals  can  grow  and  make 
the  reef  rise,  then  almost  any  thickness  may  be  made.  From 
observations  about  the  coral  regions  of  the  Pacific,  it  is  sup- 
posed that  some  of  the  reefs  have  a  thickness  of  two  or 
three  thousand  feet  or  more,  which  has  been  acquired  during 
such  a  slow  subsidence. 

The  coral  formations  of  the  Pacific  are  sometimes  broad 
reefs  around  hilly  or  mountainous  islands,  as  shown  in  tho 
annexed  sketch.  To  the  left  in  the  sketch  there  is  an  inner 

Fig.  300. 


View  of  a  high  island,  bordered  by  coral-reefs. 

reef  and  an  outer  reef,  separated  by  a  channel  of  water,  tho 
inner  of  which  (/)  is  called  a  fringing  reef,  and  tho  outer 
(£>)  a  barrier  reef.  They  are  united  in  one  beneath  tho 
water.  At  intervals  there  are  usually  openings  through  tho 
barrier  reef,  as  at  A,  h,  which  are  entrances  to  harbors.  Tho 
channels  are  sometimes  deep  enough  for  ships  to  pass  from 
harbor  to  harbor. 

Many  other  coral-reefs  stand  alone  in  the  ocean,  far  from 
any  other  lands.    The  latter  are  called  coral  islands,  or  atolls. 

Fig.  361. 


Coral  island,  or  Atoll. 

They  usually  consist  of  a  narrow  reef  encircling  a  salt- 
water lake.     The  lake  is  but  a  patch  of  ocean  enclosed  by 


CORAL-REEFS.  269 

the  reef  and  its  groves  of  palms  and 'other  tropical  plants. 

When   there   are   deep   openings   through  the   reef,   ships 

may  enter  the  lake,  or  lagoon,  as  it  is  usually  called,  and 

find   excellent   anchorage.      The   annexed 

figure  (fig.  362)  is  a  map  of  one  of  the  atolls 

of  the  Kingsmill  Islands  in  the  Pacific.   The 

reef  on  one  side — the  windward — is  wooded 

throughout;  but  on  the  other  it  has  only  a 

few  wooded  islets,  the  rest  being  bare  and 

partly  washed  by  the  tides.     At  e  there  is 

an  opening  to  the  lagoon. 

The  Paumotu  archipelago,  just  northeast  Apia,  of  the 
of  the  Society  Islands,  contains  between  70 
arid  80  coral  islands ;  the  Carolines,  with  the  Eadack,  Ealick, 
and  Kingsmill  groups  on  their  eastern  border,  as  many 
more ;  and  others  are  scattered  over  the  intervening  ocean. 
Most  of  the  high  islands  between  the  parallels  of  28°  north 
and  south  of  the  equator,  and  also  the  borders  of  the  con- 
tinents, have  their  fringe  of  coral-reefs,  unless  (1)  the  waters 
adjoining  the  coasts  are  too  deep,  or  (2)  the  bottom  is  too 
muddy,  or  (3)  the  mouths  of  rivers  are  in  the  vicinity  to 
pour  in  fresh  waters,  which  are  injurious  to  corals,  or  (4) 
cold  oceanic  currents  sweep  the  coasts.  Corals  are  limited 
by  the  parallel  of  28°,  because  they  will  not  flourish  where 
the  mean  temperature  of  the  coldest  winter  month  is  below 
68°  F. 

The  limestone  beds  made  from  corals  and  shells  are  not 
a  result  of  growth  alone,  as  in  the  case  of  the  deposits 
formed  from  microscopic  organisms,  but  of  growth  in  con- 
nection with  the  breaking  and  wearing  action  of  the  ocean's  waves 
and  currents.  Corals  and  shells,  unaided,  could  make  only  an 
open  mass  full  of  large  holes,  and  not  a  solid  rock.  There 
must  be  sand  or  fine  fragments  at  hand,  such  as  the  waters 
can  and  do  constantly  make  in  such  regions,  in  order  to  fill 
up  the  spaces  or  interstices  between  the  corals  or  shells.  If 


270  DYNAMICAL   GEOLOGY. 

there  is  clayey  or  ordinary  siliceous  sand  at  hand,  this  will 
suffice,  but  it  will  not  make  a  pure  limestone;  in  order  to 
have  the  rock  a  proper  limestone,  the  shells  and  corals  must 
be  the  source  of  the  sand  or  fine  fragments,  for  these  alono 
yield  the  needed  calcareous  material  and  cement.  The 
limestone  made  in  this  way  by  the  help  of  the  waves 
may  be,  and  often  is,  as  fine-grained  as  a  piece  of  flint  or 
any  ordinary  limestone.  In  other  cases  it  contains  some 
imbedded  fragments  in  the  solid  bed;  in  others  it  is  a  coral 
conglomerate;  and  over  still  other  large  areas  it  is  a  mass  of 
standing  corals  with  the  interstices  filled  in  solid  with  the 
sand  and  fragments.  In  some  regions  the  compact  coral 
limestone  is  an  oolite  (p.  25). 

The  pages  on  the  results  of  microscopic  life  have  explained 
one  method  by  which  the  ancient  limestones  of  the  globe 
have  been  made.  The  process  of  limestone-making  now 
going  on  through  the  agency  of  coral  animals  illustrates 
another  method,  and  far  the  most  common.  The  beds,  in 
the  case  of  these  limestones,  are  a  result  of  the  slow  growth 
of  living  corals,  crinoids,  shells,  and  the  like,  and  the  gradual 
wearing  of  the  calcareous  remains  more  or  less  completely 
to  sand  and  pebbles,  preparatory  for  consolidation. 

The  extent  of  some  of  the  modern  reefs  matches  nearly  that 
of  some  of  the  Paleozoic  reefs.  On  the  north  of  the  Feejee 
Islands  the  reef-grounds  are  5  to  15  miles  in  width.  In  New 
Caledonia  they  extend  150  miles  north  of  the  island  and  50 
miles  south,  making  a  total  length  of  400  miles.  Along 
northeastern  Australia  they  stretch  on,  although  with  many 
interruptions,  for  1000  miles.  The  modern  reef-grounds, 
although  often  of  great  length,  are,  however,  narrow,  unlike 
those  of  the  early  geological  ages.  But  this  difference  arises 
from  the  fact  that  the  regions  giving  the  requisite  depth  for 
abundant  Coral  and  Molluscan  life  are  now  of  narrow  limits, 
being  confined  to  the  borders  of  the  continents,  whereas  in 
ancient  time  the  continents  were  to  a  large  extent  sub- 


THE   ATMOSPHERE.  271 

merged  at  shallow  depths  and  afforded  the  conditions  requi- 
site for  immense  Coral,  Crinoidal,  and  Molluscan  planta- 
tions. 

II.  THE  ATMOSPHERE. 

The  following  are  some  of  the  mechanical  effects  con- 
nected with  the  movements  of  the  atmosphere. 

1.  Destructive  effects  from  the  transportation  of  sand,  dust,  etc. 
— The  streets  of  most  cities,  as  well  as  the  roads  of  the 
country,  in  a  dry  summer  day,  afford  examples  of  the  drift 
of  dust  by  the  winds.  The  dust  is  borne  most  abundantly 
in  the  direction  of  the  prevalent  winds,  and  may  in  the 
course  of  time  make  deep  beds.  The  dust  that  finds  its  way 
through  the  windows  into  a  neglected  room  indicates  what 
may  be  done  in  the  progress  of  centuries  where  circum- 
stances are  more  favorable. 

The  moving  sands  of  a  desert  or  seacoast  are  the  more 
important  examples  of  this  kind  of  action. 

On  seashores,  where  there  is  a  sea-beach,  the  loose  sands 
composing  it  are  driven  inland  by  the  winds  into  parallel 
ridges  higher  than  the  beach,  forming  drift-sand  hills.  They 
are  grouped  somewhat  irregularly,  owing  to  the  course  of 
the  wind  among  them,  and  also  to  little  inequalities  of  com- 
pactness or  to  protection  from  vegetation.  They  form 
especially  (1)  where  the  sand  is  almost  purely  siliceous, 
and  therefore  not  at  all  adhesive  even  when  wet,  and  not 
good  for  giving  root  to  grasses ;  and  (2)  on  windward  coasts. 
They  are  common  on  the  windward  side,  and  especially  the 
projecting  points,  even  of  a  coral  island,  but  never  occur  on 
the  leeward  side,  unless  this  side  is  the  windward  during 
some  portion  of  the  year.  On  the  north  side  of  Oahu  they 
are  thirty  feet  high  and  made  of  coral  eand.  Some  of  them, 
which  stand  still  higher  (owing  to  an  elevation  of  the 
island),  have  been  solidified,  and  they  show,  where  cut 
through,  that  they  consist  of  thin  layers  lapping  over  one 

24 


272  DYNAMICAL   GEOLOGY. 

another;  and  they  evince  also,  by  the  abrupt  changes  of 
direction  in  the  layers  (see  fig.  17  /),  that  the  growing  hill 
was  often  cut  partly  down  or  through  by  stormy,  and  again 
and  again  completed  itself  after  such  disasters. 

This  style  of  lamination  and  irregularity  is  characteristic 
of  the  drift-sand  hills  of  all  coasts.  On  the  southern  shore 
of  Long  Island  there  are  series  of  sand-hills  of  the  kind 
described,  extending  along  for  one  hundred  miles,  and  five 
to  thirty  feet  high.  They  are  partially  anchored  by  strag- 
gling tufts  of  grass.  The  coast  of  New  Jersey  down  to  the 
Chesapeake  is  similarly  fronted  by  sand-hills.  In  Norfolk, 
England,  between  Hunstanton  and  Weybourne,  the  sand- 
hills are  fifty  to  sixty  feet  high. 

2.  Additions  to  land  by  means  of  drift-sands. — The  drift-sand 
hills  are  a  means  of  recovering  lands  from  the  sea.     The 
appearance  of  a  bank  at  the  water's  surface  off  an  estuary  at 
the  mouth  of  a  stream  is  followed  by  the  formation  of  a 
beach,  and  then  the  raising  of  hills  of  sand  by  the  winds, 
which  enlarge  till  they  sometimes  close  up  the  estuary, 
exclude  the  tides,  and  thus  aid  in  the  recovery  of  the  land 
by  the  depositions  of  river-detritus.     Lyell  observes  that 
at  Yarmouth,  England,  thousands  of  acres  of  cultivated 
land  have  thus  been  gained  from  a  former  estuary.     In  all 
such  results  the  action  of  the  waves  in  first  forming  the 
beach  is  a  very  important  part  of  the  whole. 

3.  Destructive  effects   of    drift-sands — Dunes. — Dunes    are 
regions  of  loose  drift-sand  near  the  sea.      In  Norfolk,  Eng- 
land, between  Hunstanton  and  Weybourne,  the  drift-sands 
have  travelled  inland  with  great  destructive  effects,  burying 
farms  and  houses.     They  reach,  however,  but  a  few  miles 
from  the  coast-line,  and  were  it  not  that  the  sea-shore  itself 
is  being  undermined   by  the  waves,  and  is  thus  moving 
landward,  the  effects  would  soon  reach  their  limit. 

In  the  desert  latitudes,  drift-sands  are  more  extended  in 
their  effects. 


WATER.  273 

4.  Sand-scratches. — The  sands  carried  by  the  winds,  when 
passing  over  rocks,  sometimes  wear  them  smooth,  or  cover 
the  surface  with  scratches  and  furrows,  as  observed  by  Wm. 
P.  Blake  over  granite  rocks  at  the  Pass  of  San  Bernardino 
in  California.  Even  quartz  was  polished,  and  garnets  were 
left  projecting  upon  pedicels  of  feldspar.  Limestone  was 
so  much  worn  as  to  look  as  if  the  surface  had  been  removed 
by  solution.  Glass  in  the  windows  of  houses  on  Cape  Cod 
sometimes  has  holes  worn  through  it  by  the  same  means. 

III.  WATEE. 

The  subject  of  Water  is  here  considered  under  the  follow- 
ing heads : — 

1.  FRESH  "WATERS;  including  especially  Eivers  and  the 
smaller  Lakes,  and  also  subterranean  as  well  as  superficial 
waters. 

2.  The  OCEAN  ;  including,  along  with  the  ocean,  the  larger 
Lakes,  whether  salt  or  fresh. 

3.  FROZEN  WATERS,  or  Glaciers  and  Icebergs. 

1.  FEESH  WATEES. 
A.  SUPERFICIAL  WATERS,  OR  RIVERS. 
The  mechanical  effects  of  fresh  waters  are — 

1.  Erosion,  or  wear. 

2.  Transportation  of  earth,  gravel,  stones,  etc. 

3.  Distribution  of  the  transported  material,  and  formation 
of  fragmental  deposits. 

1.  Erosion. 

The  waters  of  rivers  descend  in  the  form  of  rain  and 
snow  from  the  clouds,  and  are  derived  by  evaporation  both 
from  the  surface  of  the  land,  with  its  lakes,  rivers,  and 
foliage,  and  from  the  ocean,  but  mostly  from  the  latter.  The 
waters  rise  into  the  upper  regions  of  the  atmosphere,  and, 


274  DYNAMICAL    GEOLOGY. 

becoming  condensed  into  drops  or  snow-flakes,  fall  over  the 
hills  and  plains.  They  gather  first  into  rills;  these,  as  they 
descend,  unite  into  rivulets;  these,  again,  if  the  region  is 
elevated  or  mountainous,  into  torrents;  torrents,  flowing 
down  the  different  mountain  valleys,  combine  with  other 
torrents  to  form  rivers;  and  rivers  from  one  mountain- 
chain  sometimes  join  the  rivers  from  another  and  make  a 
common  stream  of  great  magnitude,  like  the  Mississippi  or 
the  Amazon. 

The  Mississippi  has  its  tributaries  among  all  the  central 
heights  of  the  Great  Eocky  Mountain  chain,  throughout  a 
distance  of  1000  miles,  or  between  the  parallels  of  35°  N. 
and  50°  N. ;  and  still  another  set  of  tributaries  gather  in 
waters  from  the  Appalachian  chain,  between  western  New 
York  and  Alabama.  Bills,  rivulets,  torrents,  and  rivers 
combine  over  an  area  of  millions  of  square  miles  to  make 
the  great  central  trunk  of  the  North  American  continent. 

The  amount  of  water  poured  each  year  into  the  ocean  by 
the  Mississippi  averages  19  £  trillions  (19,500,000,000,000) 
cubic  feet,  varying  from  11  trillions  in  dry  years  to  27 
trillions  in  wet  years.  This  amount  is  about  one-quarter  of 
that  furnished  by  the  rains,  the  rest  being  lost  mostly  by 
direct  evaporation,  but  also  in  part  by  absorption  into  the 
soil  and  by  contributing  to  the  growth  of,  vegetation. 

Erosion,  or  wear,  goes  on  wherever  the  waters  have 
motion.  The  rain-drop  makes  an  impression  (fig,  21) 
where  it  falls;  the  rill  and  rivulet  carry  off  light  sand  and 
deepen  their  bed,  as  may  be  seen  on  any  sand-bank  or  by 
many  a  roadside;  torrents  work  with  far  greater  power, 
tearing  up  rocks  and  trees  as  they  plunge  along,  and,  in  the 
course  of  time,  making  deep  gorges  or  valleys  in  the  moun- 
tain-slopes ;  and  rivers,  especially  in  periods  of  flood,  hurry 
on  with  vast  power,  making  wider  valleys  over  the  breadth 
of  a  continent. 

The  slopes  of  a  lofty  mountain,  exposed  through  ages  to 


WATER.  275 

the  action  described,  finally  become  reduced  to  a  series  of 
valleys  and  ridges,  and  the  summit  often  to  towering  peaks 
and  crested  heights, — all  these  effects  originating  in  the  fall 
of  rain-drops  or  snow-flakes. 

The  tendency  of  many  rocks  to  decompose,  aids  the 
waters  in  producing  their  mechanical  effects. 

Where  the  stream  has  a  rapid  descent,  and  is  therefore  a 
torrent,  it  plunges  on  with  great  violence  and  erodes  mainly 
along  its  bottom.  Lower  down  the  mountain,  where  the 
slope  of  its  bed  is  gentle,  it  becomes  more  quiet,  and  exca- 
vates but  slightly,  if  at  all,  at  bottom.  In  its  floods,  how- 
ever, it  spreads  beyond  its  banks  and  tears  away  the  earth 
or  rocks,  encroaching  on  the  hills  either  side,  and  making 
for  itself  a  broad  flat,  or  flood-plain.  As  the  floods  cease, 
the  stream  becomes  again  confined  to  its  channel.  Every 
river  has  thus  its  channel  for  the  dry  season,  and  its  flood- 
plain  which  it  covers  in  times  of  overflowing. 

The  great  rivers  of  the  continents,  as  well  as  the  stream- 
lets along  roadsides,  illustrate  this  subject.  Wherever,  in 
countries  that  have  rain,  there  is  a  ridge,  be  it  small  or 
large,  there  are  gullies,  or  gorges,  or  valleys;  and  if  any  of 
its  streams  are  followed  up  to  their  head,  there  will  be 
found,  first,  the  channel  and  its  bordering  flood-plain;  then 
the  narrower  valley  with  the  hurrying  torrent,  receiving 
smaller  torrents  along  its  course ;  then,  towards  the  top,  the 
torrent  dwindling  to  a  rivulet,  or,  if  the  summit  is  nearly 
flat  and  wooded,  there  may  be  at  top  wet  swampy  land  or 
lakes. 

A  cascade  usually  occurs  on  a  rapid  stream,  where  in  the 
course  of  it  there  is  a  hard  bed  of  rock  overlying  a  soft  one. 
The  hard  bed  resists  wear,  while  the  soft  one  below  yields 
easily:  thus  a  plunge  begins,  which  increases  in  force  as  it 
increases  in  extent.  The  rills  and  rivulets  made  by  a  shower 
of  rain  along  roadsides  or  sand-banks  often  illustrate  also 
this  feature  of  the  great  mountain  streams. 
24» 


276 


DYNAMICAL   GEOLOGY. 


When  the  rocks  underlying  a  region  are  nearly  horizon- 
tal, the  valleys  cut  by  the  rivers  have  usually  bold  rocky  sides. 
In  many  parts  of  the  EockjT  Mountains  the  streams  have 
worked  their  way  down  through  the  rocks  for  hundreds, 
and  at  times  even  thousands,  of  feet.  Such  a  place  is  often 
called  a  canon  (pronounced  as  if  spelled  canyon). 

These  canons  are  of  wonderful  magnitude  and  depth  on 
the  Colorado  Eiver,  over  the  west  slope  of  the  Eocky 
Mountains,  between  longitude  111°  W.  and  115°  W.  For 

Fig.  363. 


CaSon  of  the  Colorado  near  its  junction  with  Green  River. 

300  miles  there  is  a  continuous  caSon,  3000  to  6000  feet 
deep.     The  annexed  sketch,  furnished  the  author  by  Dr. 


WATER.  277 

Newberry  (the  Geologist  of  the  Expedition,  under  Lieuten- 
ant J.  C.  Ives,  that  surveyed  this  region  and  first  made 
known  the  facts),  represents  the  great  plain  of  the  Colorado 
region,  with  its  deep  vertical  cuts  opening  down  to  running 
water.  This  water  is  the  Colorado  Eiver,  and  the  opening 
that  looks  so  much  like  a  mere  crack  in  the  rocks  has  a 
depth  at  the  place  of  about  3000  feet.  The  deep  gorge  is 
the  result,  as  stated  by  Dr.  dewberry,  of  erosion  by  the 
stream,  which  is  still  continuing  its  wearing  action.  The 
isolated  flat-topped  hills  and  turreted  rocks  in  the  distance 
are  portions  of  strata  that  once  covered  the  other  rocks, 
being  all  of  the  upper  formations  that  the  eroding  waters 
have  left, 

The  rocky  gorge,  7  miles  long  and  200  to  250  feet  deep, 
in  which  the  Niagara  Eiver  flows  in  violent  rapids  after  its 
plunge  at  the  great  fall,  is  believed  with  reason  to  have  been 
made  by  the  waters,  and  mainly  through  the  action  of  the 
plunging  stream  at  the  fall.  Every  year  rocks  are  under- 
mined and  tumbled  down  idto  the  depths  below,  and  thus 
the  position  of  the  fall  is  slowly  changing,  moving  higher- 
and  higher  up  stream  with  the  successive  years.  The  rock, 
for  half  the  height  of  the  fall,  or  80  feet,  is  of  hard  lime- 
stone; but  the  lower  half  is  of  soft  shale,  and,  being  easily 
worn  away  by  the  waters,  it  undermines  the  limestone  and 
thus  assists  in  the  movement. 

2.  Transportation  by  rivers,  and  distribution  of  transported 
material. 

1.  Fact  of  transportation. — It  has  been  stated  that  the 
massive  mountains  have  been  eroded  into  valleys  and  ridges 
by  running  water.  The  material  worn  out  has  been  trans- 
ported somewhere  by  the  same  waters. 

Part  of  the  transported  material  in  all  such  operations 
goes  to  form  the  great  alluvial  plains  that  occupy  the  river- 
valleys  throughout  their  course.  Part  is  carried  on  to  the 


278  DYNAMICAL   GEOLOGY. 

sea  into  which  the  river  empties,  when  it  meets  the  counter- 
acting waves  and  currents  and  is  distributed  for  the  most 
part  along  the  shores,  filling  estuaries  or  bays,  or  making 
deltas,  and  extending  the  bounds  of  the  land. 

Thus  the  mountains  of  a  continent  are  ever  on  the  move 
•seaward,  and  contribute  to  the  enlargement  of  the  seashore 
plains.  The  continent  is  losing  annually  in  mean  height, 
but  gaining  in  width  or  extent  of  dry  land. 

2.  The   transporting   power   of   water. — The    transporting 
power  of  running  water  is  very  great  when   the  flow  is 
rapid.     Doubling  the  rate  of  flow  increases  sixty-four  times 
the  force  of  the  water.     Large  stones  and  masses  of  rocks 
are  torn  up  and  moved  onward  by  the  mountain-torrent; 
pebbles,  when  the  current  runs  but  a  few  miles  per  hour ; 
and  at  slower  rates,  gravel,  sand,  or,  when  very  slow,  only 
fine  clay.    Hence,  as  a  stream  loses  in  rapidity  of  movement, 
it  leaves  behind  the  coarser  material,  and  carries  only  the 
finer;  if  the  rate  becomes  very  slow,  it  drops  the  gravel  or 
the  sand,  and  bears  on  only  the  finest  earth  or  clay. 

Consequently,  where  the  current  is  swift,  the  bottom  (and 
the  shores  also  wherever  the  current  strikes  them)  is  stony 
or  pebbly;  and  Avhere  the  water  is  still,  or  nearly  so,  the 
bottom  and  shores  are  muddy. 

The  larger  part  of  the  transportation  by  rivers  is  done  in 
their  seasons  of  flood.  Then  it  is  that  streams  are  muddy 
with  the  earth  they  are  bearing  along. 

3.  Wearing  action  on  the  transported  material. — The  stones 
are  not  only  transported  by  the  waters,  but  by  the  mutual 
friction  thus  produced  they  are  made  into  rounded  stones 
and  reduced  to  pebbles  and  earth.     Nearly  all  the  rounded 
stones,  gravel,  and  earth  of  fields  and  gardens  over  the 
globe,  and  also  the  material  of  all  geological  formations,  has 
been  made  out  of  pre-existing  solid  rocks  by  the  wearing 
action  of  waters, — either  those  of  streams  over  the  land,  or 
those  of  the  ocean. 


WATER.  279 

The  finer  transported  material  is  called  detritus  (from  the 
Latin  for  worn  out),  and  also  silt.  The  rounded  stones  are 
termed  boulders. 

4.  Amount  of  material  transported. — The  amount  of  tran- 
sported material  varies  with  the  size  and  current  of  the 
rivers  and  the  kind  of  country  they  flow  through.     The 
Mississippi  carries  to  the  Gulf  of  Mexico,  according  to  Hum- 
phreys &  Abbot,  annually,  on  an  average,  812,500,000,000 
pounds  of  silt, — equal  to  a  mass  one  square  mile  in  area  and 
241  feet  deep, — and  its  bottom-waters  push  on  enough  more 
to  make  the  241  feet  268  feet.     The  total  annual  discharge 
of  silt  by  the  Ganges  has  been  estimated  at  6.368,000,000 
cubic  feet. 

5.  Alluvial  formations. — The  deposits  made  by  the  tran- 
sported material  which  now  constitute  the  alluvial  plains  of 
the  river-valleys  cover  a  very  large  part  of  a  continent, 
since  rivers  or  smaller  streams  are  almost  everywhere  at 
work.      They  are  made  up  of  layers  of  pebbles  or  gravel, 
and  of  earth,  silt,  or  clay,  especially  of  these  finer  mate- 
rials.   Some  logs,  leaves,  and  bones  occur  in  them ;  but  these 
are  rare ;  for  whatever  floats  down  stream  is  widely  scat- 
tered by  the  waters,  and  to  a  great  extent  destroyed  by 
wear  and  decay. 

6.  Estuary   and  delta  formations. — The    detritus-material 
discharged  by  the  river  at  its  mouth  tends  to  fill  up  the  bay 
into  which  it  empties,  and  make  wide  flats  on  its  borders,  and 
thus  contract  it  to  the  breadth  merely  of  the  river-current. 

"Where  the  tides  are  feeble  and  the  river  large,  the  deposits 
about  the  mouth  of  the  stream  gradually  encroach  on  the 
ocean,  and  make  great  plains  and  marshy  flats,  which  are 
intersected  by  the  many  mouths  of  the  river  and  a  network 
of  cross-channels.  Such  a  formation  is  called  a  delta. 
Figure  364  represents  the  delta  of  the  Mississippi,  the  white 
lines  being  the  water-channels,  and  the  black  the  great  allu- 
via] plains.  The  delta  properly  commences  below  the  mouth 


280 


DYNAMICAL   GEOLOGY. 


of  Red  Kiver,  where  the  Atchafalaya  bayou,  or  side-channel 
of  the  river,  begins.    The  whole  area  is  about  12,300  square 


miles;  about  one-third  is  a  sea-marsh,  only  two-thirds  lying 
above  the  level  of  the  Gulf. 

The  deltas  of  the  Nile,  Ganges,  and  Amazon  are  similar 
in  general  features  to  that  of  the  Mississippi. 


281 


The  detritus  poured  into  the  ocean  where  the  tides  or 
currents  are  strong,  and  a  considerable  part  of  that  where 
the  tides  are  feeble,  goes  to  form  seashore  flats  and  sand- 
banks and  off-shore  deposits.  In  their  formation  the  ocean 
takes  part  through  its  waves  and  currents;  and  hence  they 
are  more  conveniently  described  in  connection  with  the 
remarks  on  oceanic  action. 

B.  SUBTERRANEAN  WATERS. 

1.  Origin  and  course  of  subterranean  waters. — A  part  of  the 
waters  that  fall  on  the  earth's  surface — on  its  mountains  as 
well  as  its  plains — sinks  through  the  ground  and  often 
penetrates  to  unknown  depths  between  the  strata  or  their 
layers.  Such  under-ground  waters  become  under-ground 
streams  ;  and,  as  their  channels  are  surrounded  by  rocks,  the 
water  flows  actually  in  a  tube.  When,  therefore,  they  have 
their  source  in  elevated  regions,  the  pressure  increases  with 
the  descent,  and  wherever  an  opening  in  the  country  below 
gives  them  a  chance  of 
escape,  they  often  come  out  Flg>  365' 

with  great  force.  By  boring 
down  through  the  rocks, 
such  an  under-ground 
stream  may  be  struck  in 
almost  any  region,  and  fre- 
quently the  water  will  rise 
and  rush  out  of  the  opening 

in     a    jet    Of    great     height.    Section  illnstrating  the  origin  of  Artesian  Well8. 

In  fig.  365  the  under-ground  waters  are  supposed  to  enter  at 
a,  along  a  clayey  layer  (for  clayey  layers  hold  the  water, 
while  it  will  soak  through  a  sandy  one) ;  it  escapes  by  the 
boring  b  c,  and  is  thrown  up  in  a  jet  to  d.  There  is  so  much 
friction  along  the  bed  of  the  stream  in  the  course  of  its 
descent,  that  the  height  of  the  jet  is  always  much  less  than 
the  whole  descent,  or  b  e. 


282  DYNAMICAL   GEOLOGY. 

Such  wells  are  usually  called  Artesian  wells  or  borings,  from 
the  district  of  Artois  in  France,  where  they  were  early 
made.  The  Artesian  well  of  Grenelle  in  Paris  is  2000  feet 
deep.  One  at  St.  Louis  has  a  depth  of  2200  feet;  another 
at  Louisville  is  over  2000  feet.  Such  wells  are  used  for 
agricultural  purposes  in  California,  and  for  manufacturing 
in  various  cities,  as  New  York,  New  Haven,  etc. 

The  under-ground  waters  often  gush  out  along  a  seashore, 
or  from  beneath  the  sea ;  and  sometimes  in  so  great  volume 
that  vessels  at  certain  seasons  are  enabled  to  take  in  fresh 
water  from  alongside  while  lying  off  in  a  harbor. 

They  flow  and  have  cascades  in  many  caverns,  as  in  the 
Mammoth  Cave,  Kentucky,  the  Adelberg  Cave  near  Trieste 
in  Austria,  and  many  others.  In  some  cases  they  come  out 
to  the  surface  in  sufficient  volume  to  turn  a  mill,  and  are  set 
to  work  immediately  on  their  showing  themselves. 

2.  JErosion. — Subterranean  waters  have  eroding  and  tran- 
sporting power,  as  well  as  those  of  the  land,  and  may  exca- 
vate large  channels. 

3.  Land-slides. — Land-slides  are  of  different  kinds : — 

(1.)  The  sliding  of  the  surface  earth  or  gravel  of  a  hill 
down  to  the  plain  below.  This  effect  may  be  caused  by  the 
waters  of  a  severe  storm  wetting  the  material  deeply  and 
giving  it  greatly  increased  weight,  besides  loosening  its  attach- 
ment to  the  more  solid  mass  below. 

(2.)  The  sliding  down  a  declivity  to  the  plain  below  of 
the  upper  layer  of  a  rock-formation.  This  may  happen 
when  this  upper  layer  rests  on  a  clayey  or  sandy  layer  and 
the  latter  becomes  very  wet  and  greatly  softened  by  the 
waters ;  the  upper  layer  slides  down  on  the  softened  bed. 

(3.)  The  settling  of  the  ground  over  a  large  area.  This 
may  take  place  when  a  layer  of  clay  or  loose  sand  becomes 
wet  and  softened  by  percolating  waters,  and  then  is  pressed 
out  laterally  by  the  weight  of  the  superincumbent  layers 


WATER.  283 

But  this  effect  cannot  be  produced  unless  there  happens  to 
be  a  chance  for  the  wet  layer  to  move  or  escape  laterally. 

2.  THE  OCEAN. 

The  ocean  is  vast  in  extent  and  vast  in  the  power  which 
it  may  exert.  But  its  mechanical  work  in  Geology  is  mostly 
confined  to  its  coasts  and  to  soundings,  where  alone  material 
exists  in  quantity  within  reach  of  the  waves  or  currents. 
In  ancient  time,  when  the  continents  were  nearly  flat  and  to 
a  great  extent- submerged  at  shallow  depths,  this  work  was 
performed  simultaneously  over  a  large  part  of  their  surface, 
and  strata  nearly  of  continental  extent  were  sometimes 
formed.  In  the  present  age,  oceanic  action  is  confined  to 
the  borders  of  the  continents. 

The  mechanical  effects  of  the  ocean  are  produced  by  its 
waves  and  currents. 

1.  Erosion  and  Transportation. 

1.  Waves. — (1.)  General  action.— The  oceanic  waves  are  a 
constant  force.  Night  and  day,  year  in  and  year  out,  with 
hardly  an  intermission,  they  break  against  the  beaches  and 
rocks  of  the  coasts; — sometimes  gently,  sometimes  in  heavy 
plunges  that  have  the  force  of  a  Niagara  of  almost  unlimited 
breadth.  The  gentlest  movements  have  some  grinding 
action  on  the  sands,  while  the  heaviest  may  dislodge  and 
move  along  up  the  shores  rocks  many  tons  in  weight. 
Niagara  wastes  its  power  by  falling  into  an  abyss  of  waters : 
while  in  the  case  of  the  waves  the  rocks  are  bared  anew  for 
each  successive  plunge.  Cliffs  are  undermined,  rocks  are  worn 
to  pebbles  and  sand,  and  sand  ground  to  the  finest  powder. 
Rocky  headlands  on  windward  coasts  are  especially  exposed 
to  wear,  since  they  are  open  to  the  battering  force  from 
different  directions. 

(2.)  Level  of  greatest  eroding  action. — The  eroding  action 


284  DYNAMICAL   GEOLOGY. 

is  greatest  for  a  short  distance  above  the  height  of  half-tide, 
and,  except  in  violent  storms,  it  is  almost  null  below  low-tido 
level.     Figure  366  represents 
in   profile   a   cliff,  having   its 
lower  layers,  near  the  level  of 
low-tide,  extending  out  as  a 
platform  a  hundred  yards  wide. 
As  the  tide  commences  to  move 
in,  the  waters  while  still  quiet 

swell  over  and  cover  this  platform,  and  so  give  it  their  pro- 
tection ;  and  the  force  of  wave-action,  which  is  greatest 
above  half-tide,  is  mainly  expended  near  the  base  of  the 
cliff,  just  above  the  level  of  the  platform. 

(3.)  Action  landward. — Waves  on  shallow  soundings  have 
some  transporting  power;  and,  as  they  always  move  toward 
the  land,  their  action  is  landward.  They  thus  beat  back, 
little  by  little,  any  detritus  in  the  waters,  preventing  that 
loss  to  continents  or  islands  which  would  take  place  if  it 
were  carried  out  to  sea. 

(4.)  Effect  on  outline  of  coasts — No  excavation  of  narrow 
valleys. — As  the  action  of  waves  on  a  coast  tends  to  wear 
away  headlands,  and  at  the  same  time  to  fill  up  bays  with 
detritus,  the  general  result  will  be  to  render  the  outline 
more  regular  or  even.  There  is  nowhere  a  tendency  to 
excavate  narrow  valleys  into  a  coast,  like  those  occupied  by 
rivers.  Such  valleys  are  made  by  the  waters  of  the  land ; 
for  the  ocean  can  work  at  valley-making  only  when  it  has 
already  an  open  channel  for  the  waters  to  pass  through, 
and  then  the  valleys  are  of  very  great  width.  If  a  continent 
were  sinking  slowly  in  the  ocean,  or  rising  slowly  from  it, 
wave-action  would  still  be  attended  by  the  same  results;  for 
each  part  of  the  surface  would  be  successively  a  coast-line, 
and  over  each  there  would  be  the  same  wearing  away  of 
headlands  and  filling  of  bays,  instead  of  the  excavation  of 
valleys. 


WATER.  285 

2.  Tidal  currents. — Tidal  currents  often  have  great  strength 
when  the  tide  moves  through  channels  or  among  islands, 
and  consequently  are  a  means  of  erosion  and  transportation 
in  daily  action  wherever  there  is  mud  or  sand  within  their 
reach,  as  is  usually  the  case  in  the  vicinity  of  the  land. 

The  out-flowing  current,  or  that  connected  with  the  ebbing 
tide,  is  deeper  in  its  action  and  has,  therefore,  more  excavating 
and  more  transporting  power  than  the  in-flowing,  or  that  of 
the  incoming  tide.  The  latter  moves  on  as  a  great  swelling 
wave,  and  fills  the  bays  much  above  their  natural  level;  but 
the  out-flowing  current  begins  along  the  bottom  in  bays 
before  the  tide  is  wholly  in,  owing  to  the  accumulation  of 
waters,  and  when  the  tide  changes  it  adds  to  the  strong 
current-movement  already  in  progress. 

The  piling  up  of  the  waters  in  a  bay  by  the  tides,  or  by 
storms,  produces,  especially  if  the  entrance  is  not  very 
broad,  a  strong  out-flowing  current  at  bottom,  which  tends 
to  keep  the  channel  deep  and  clear  of  obstructions. 

The  bore  or  eagre  of  some  great  rivers  is  a  kind  of  tidal 
flow  up  a  stream.  It  is  produced  when  the  regular  rise  of 
the  tide  in  the  bay  at  the  mouth  of  the  river  is  prevented 
by  the  form  of  the  entrance  and  its  sand-banks,  together 
with  the  outflow  of  the  river,  so  that  the  waters  are  for  a 
while  prevented  from  entering  until,  finally,  all  of  one  tide 
rush  in  at  once,  or  in  a  few  great  waves.  The  eagres  of 
the  Amazon,  the  Hoogly  in  India  (one  of  the  mouths  of  the 
Ganges),  and  the  Tsien-tang  in  China,  are  among  the  most 
remai-kable.  In  the  case  of  the  Tsien-tang,  the  water  moves 
up  stream  in  one  great  wave,  plunging  like  an  advancing 
cataract,  4  or  5  miles  broad  and  30  feet  high,  at  a  rate  of  25 
miles  an  hour.  The  boats  in  the  middle  of  the  stream 
simply  rise  and  fall  with  the  passage  of  the  wave,  being 
pushed  forward  only  a  short  distance ;  but  along  the  shores 
there  is  great  devastation,  the  banks  being  worn  away  and 
animals  often  surprised  and  destroyed. 


286  DYNAMICAL   GEOLOGY. 

3.  Currents  made  by  winds. — There  are  also  currents  pro- 
duced by  winds,  especially  when  there  are  long  storms,  or 
when  the  winds  blow  for  months  in  one  direction.     Tho 
currents  thus  made  have  but  little  depth.     Sweeping  by  an 
island,  they  transport  from  one  place  to  another  in  their 
course  more  or  less  of  the  sand  of  the  shores,  and  the  same 
sand  may  be  in  part  carried  back  again  when  the  season 
changes  to  that  in  which  the  wind  blows  from  the  opposite 
direction.     Other  portions  of  detritus  may  be  carried  by 
them  away  from  the  island  and  distributed  in  the  deeper 
waters. 

4.  Great  oceanic  currents. — The  great  currents  of  the  ocean, 
like  that  called  the  Gulf  Stream,  are  for  the  most  part  so 
distant  from  the  borders  of  the  continents  that  little  detritus 
comes  within  their  reach.     As  these  currents  have  great 
depth, — often  a  thousand  feet  or  more, — their  course  is  deter- 
mined by  the  deep-water  slopes  of  the  submerged  border  of 
a  continent,  so  that  when  the  submerged  border  is  shallow 
for  a  long  distance  out  (as  off  New  Jersey  and  Virginia, 
where  this  long  distance  is  even  50  to  80  miles),  the  current 
is  equally  remote,  and  exerts  very  feeble  if  any  action  near 
the   shores.     Wherever  it  actually  sweeps   close   along   a 
coast,  it  will  bear  away  some  detritus  to  drop  it  over  the 
bottom  in  the  neighboring  waters. 

The  oceanic  currents  flowing  from  polar  seas  produce 
important  effects  by  means  of  the  icebergs  which  they  bear 
into  warmer  latitudes.  These  icebergs  are  freighted  with 
thousands  of  tons  of  earth  and  stones;  and  wherever  they 
melt,  they  drop  the  whole  to  the  ocean's  bottom.  The  sea 
about  the  Newfoundland  banks  is  one  of  the  regions  of 
the  melting  bergs ;  and  there  is  no  doubt  that  vast  submarine 
unstratified  accumulations  of  such  material  have  been  there 
made  by  this  means.  It  has  been  suggested  that  the  banks 
may  have  been  thus  formed. 


WATER.  287 

2.  Distribution  of  material,  and  the  formation  of  marine  and 
fluvio-marine  deposits. 

1.  Origin  of  material. — The  material  used  by  the  waves 
and  currents  is  either — (1)  the  stones,  gravel,  sand,  or  earth 
produced  by  the  wear  of  coasts;  or  (2)  the  detritus  brought 
down  by  rivers  and  poured  into  the  ocean,  as  explained  on 
page  281. 

The  latter  in  the  present  age  is  vastly  the  most  important. 
But  in  the  earlier  geological  ages,  when  the  dry  land  was 
of  very  small  extent,  rivers  were  small  and  were  but  a  feeble 
agency.  The  ocean  had  then  vastly  greater  advantages 
than  now,  because,  as  stated  on  page  84,  the  continents 
were  mostly  submerged  at  very  shallow  depths,  or  lay  near 
tide-level  within  reach  of  the  waves  and  currents. 

2.  Forces  in  action. — In  the  distribution  of  this  material, 
the  waves  and  marine  currents  may  work  alone,  in  the  man- 
ner explained  on  the  preceding  pages,  or  in  conjunction 
with  river-currents  wherever  these  exist. 

3.  Marine  formations. — The  marine  formations  are  of  the 
following  kinds : — 

(1.)  E each-accumulations. — Beaches  are  made  of  the  mate- 
rial borne  up  the  shores  by  the  waves  and  tides  and  left  above 
tide-level.  This  material  consists  of  stones  or  pebbles,  sand, 
mud,  earth,  or  clay.  It  is  coarse  when  the  waves  break 
heavily,  because,  although  trituration  to  powder  is  going  on 
at  all  times,  the  powerful  wave-action  and  the  undercurrent 
carry  off  the  finer  material  into  the  off-shore  shallow 
waters,  where  it  settles  over  the  bottom  or  is  distributed  by 
currents.  It  is  fine  where  the  waves  are  gentle  in  movement, 
as  in  sheltered  bays,  the  triturated  material  remaining  in 
such  places  near  where  it  is  made,  and  often  being  the  finest 
of  mud. 

(2.)  Sand-banks,  or  reefs— Shallow-water  accumulations.— 
Shallow-water  accumulations  may  be  produced  in  bays, 


288  DYNAMICAL   GEOLOGY. 

estuaries,  or  the  inner  channels  of  a  coast,  and  over  the 
bottom  outside.  They  consist  usually  of  coarse  or  fine  sand 
and  earthy  detritus,  but  may  include  pebbles  or  stones  when 
the  currents  are  strong.  The  material  constituting  them  is 
derived  from  the  land  through  the  triturating  and  tran- 
sporting action  of  the  waves  and  currents.  The  accumula- 
tions may  increase  under  wave-action  in  shallow  water, 
until  they  approach  or  rise  above  low-tide  level,  and  then 
they  form  sand-banks.  Such  sand-banks  keep  their  place 
in  the  face  of  the  waves,  for  the  same  reason  as  the  platibrm 
of  rock  mentioned  on  page  284  and  illustrated  in  fig.  366. 

(3.)  Fluvio-marine  formations. — Most  of  the  accumula- 
tions in  progress  on  existing  shores,  whether  sand-banks,  or 
estuary  or  off-shore  deposits,  especially  about  well-watered 
continents,  contain  more  or  less  of  river-detritus,  and  are 
modified  in  their  forms  by  the  action  of  river-currents. 
Along  the  whole  eastern  coast  of  the  United  States  south 
of  New  England,  and  on  all  the  borders  of  the  Gulf  of 
Mexico,  the  formations  in  progress  are  mainly  fluvio-marine, 
— that  is,  the  combined  result  of  rivers  and  the  ocean.  The 
coast-region  on  the  continent  is  now  slowly  widening 
through  this  means,  and  has  been  widening  for  an  indefinite 
period.  This  coast-region  is  low,  flat,  often  marshy,  full  of 
channels  or  sounds;  and  facing  the  ocean  there  is  a  barrier 
reef,  made  of  sand. 

The  rivers  pour  out  their  detritus  especially  during  their 
floods,  and  the  ocean's  waves  and  currents  meet  it  as  the 
tide  sets  in  with  a  counter-action,  or  one  from  the  seaward; 
and  between  the  two  the  waters  lose  in  rate  of  flow  and 
drop  the  detritus  over  the  bottom.  When  the  river  is  very 
large  and  the  tides  feeble,  the  banks  and  reefs  extend  far 
out  to  sea.  The  Mississippi  thus  stretches  its  many-branched 
mcuth  (p.  280)  many  miles  into  the  Gulf.  When  the  tide 
is  high,  sand-bars  are  formed;  and  the  higher  the  tides  the 
closer  are  the  sand-bars  to  the  coast.  When  the  stream  is 


small,  the  ocean  may  throw  a  sand-bank  quite  across  its 
mouth,  so  that  there  shall  be  no  egress  to  the  river-waters 
except  by  percolation  through  the  sand ;  or,  if  a  channel  be 
left  open,  it  may  be  only  a  shallow  one. 

3.  Structure  of  the  formations. 

Beach-formations  are  very  irregular  in  stratification.  The 
layers — as  shown  in  figure  17e,  page  31 — have  but  little 
lateral  extent,  and  change  in  character  every  few  feet. 
They  often  include  patches  of  stones,  as  well  as  pebbles  and 
sand. 

The  sand-banks  and  reefs  made  along  a  coast  have  much 
more  regular  stratification,  and  are  mostly  composed  of  sand 
with  some  beds  of  pebbles.  They  often  vary  much  every 
mile  or  every  few  miles. 

Those  beds  that  are  formed  in  shallow  waters,  as  in  bays 
or  in  the  off-shore  waters,  retain  a  uniformity  of  stratifica- 
tion over  much  larger  areas,  and  may  consist  of  pebbles, 
sand,  or  finer  earth.  The  extent  and  regularity  of  level  of 
the  submerged  area  will  determine  in  a  great  degree  the 
extent  to  which  the  uniformity  of  stratification  may  extend; 
and  in  this  respect  the  former  geological  ages,  as  observed 
on  page  287,  had  greatly  the  advantage  of  the  present. 

Ripple-marks  (figure  18,  p.  32)  are  made  by  the  spread  of 
the  waters  in  a  wave  up  a  beach,  or  by  wave-action  on  the 
bottom  within  soundings  where  the  depth  does  not  exceed 
69  or  80  fathoms.  Rill-marks  (fig.  19)  are  produced  when 
the  return  waters  of  a  tide,  or  of  a  wave  that  has  broken 
on  a  beach,  flow  by  an  obstacle,  as  a  shell  or  pebble,  and  are 
piled  up  a  little  by  it  so  as  to  be  made  to  plunge  over  it  and 
so  erode  the  sands  for  a  short  distance  below  the  obstacle. 
The  oblique  lamination  in  a  layer,  or  ebb-and-flow  structure, 
ix-sults  from  the  rapid  inward  movement  of  the  tide,  or  of  a 
current,  over  a  sandy  bottom :  it  makes  a  series  of  inclined 
layers  by  the  piling  action;  when  the  movement  ceases,  the 


290  DYNAMICAL   GEOLOGY. 

detritus  will  deposit  horizontally  for  a  while ;  and  afterward 
the  same  inward  movement  may  be  repeated,  producing 
anew  the  oblique  lamination. 

The  imbedded  shells  and  other  animal  relics  in  a  beach 
are  worn  or  broken ;  those  in  the  bays  or  off-shore  shallow 
waters  out  of  the  reach  of  the  waves  may  be  unbroken,  or 
may  lie  as  they  did  when  living ;  but  if  the  waters  are  not 
so  deep  but  that  the  shells  or  corals  are  exposed  to  wave- 
action,  they  may  be  broken  or  worn  to  powder,  and  enter  in 
this  state  into  the  formation  in  progress.  See  (page  85)  the 
remarks  on  the  formation  of  limestone  from  shells  or  corals. 
In  the  sands  of  beaches  near  low-tide  level,  borings  of  Sea- 
worms,  or  of  some  Mollusks  or  Crustaceans,  may  exist. 


3.  FREEZING  AND  FKOZEJST  WATEBS. 

A.  FREEZING  WATER. 

As  water  in  the  act  of  freezing  expands,  the  freezing  pro- 
cess, when  taking  place  in  the  seams  of  rock,  opens  the 
seams  and  tears  masses  asunder.  This  kind  of  action  is 
especially  destructive  in  the  case  of  rocks  that  are  much 
fissured,  or  intersected  by  joints,  or  that  have  a  slaty  or 
laminated  structure.  As  the  action  continues  through  suc- 
cessive years  and  centuries,  it  may  result  in  great  accumu- 
lations of  broken  stone.  The  slope,  or  talus,  of  fragments 
at  the  foot  of  bluffs  of  trap  or  basalt  is  often  half  as  high  as 
the  bluff  itself.  In  tropical  countries,  bluffs  have  no  such 
masses  of  ruins  at  their  base. 

Granular  rocks,  whether  crystalline  or  not,  when  they 
readily  absorb  water,  lose  their  surface-grains  by  the  same 
freezing  process.  Granite,  as  well  as  porous  sandstones, 
may  thus  be  imperceptibly  turning  to  dust,  earth,  or  gravel 
In  Alpine  regions  this  action  may  be  incessant. 


GLACIERS.  291 

B.  FROZEN  WATER. 

The  effects  of  ice  and  snow  are  conveniently  considered 
under  three  heads: — 1.  The  ice  of  lakes  and  rivers;  2. 
Glaciers;  3.  Icebergs. 

1.  ICE  OF  LAKES  AND  RIVERS. 

The  ice  of  lakes  and  rivers  often  freezes  about  stones  along 
their  shores,  making  them  part  of  the  mass;  and  other  stones 
sometimes  fall  on  the  surface  from  overhanging  bluffs.  In 
times  of  high-water,  or  floods,  the  ice,  rising  with  the 
waters,  may  carry  its  burden  high  up  the  shores,  or  over 
the  flooded  flats,  to  leave  them  there  as  it  melts;  or,  if 
within  reach  of  the  current,  it  may  transport  the  stones  far 
down  stream.  This  is  a  common  method  of  transportation 
by  ice.  Large  accumulations  of  boulders  are  sometimes 
made  by  this  means  on  the  shores  of  lakes  far  above  the 
ordinary  level  of  the  waters. 

2.  GLACIERS. 

1.  Glaciers  are  ice-streams,  or  rivers  in  which  the  moving 
material  is  frozen  instead  of  liquid  water. 

Like  large  rivers,  they  have  their  sources  in  high  moun- 
tains, derive  their  waters  from  the  clouds,  and  descend  along 
the  valleys;  but  the  mountains  are  such  as  take  snow  from 
the  clouds  instead  of  rain,  because  of  their  elevation.  They 
rise  only  in  those  mountains  that  receive  annually  a  large 
supply  of  snow  from  the  clouds ;  for  the  snow  must  accumu- 
late to  a  great  depth. 

Like  large  rivers,  many  tributary  streams  coming  from 
the  different  valleys  unite  to  make  the  great  stream. 

As  with  rivers,  their  movement  is  owing  to  gravity,  or  to 
the  weight  of  the  material ;  but  the  average  rate  of  motion, 
instead  of  being  some  miles  an  hour,  is  generally  but  8  to 
10  inches  a  day,  or  a  mile  in  15  to  25  years. 


292  DYNAMICAL   GEOLOGY. 

As  with  rivers,  the  central  portions  move  most  rapidly, 
the  sides  and  bottom  being  retarded  by  friction ;  but  the 
difference  of  rate  between  the  sides  and  bottom  is  far 
greater  in  glaciers  than  in  rivers. 

The  snow  of  the  mountain-tops,  which  is  perhaps  hun- 
dreds of  feet  deep,  becomes  compacted  and  converted  into 
ice  mainly  by  its  own  weight;  and  thus  the  glacier  begins. 
As  it  starts  on  its  course,  the  clouds  furnish  new  snows  to 
keep  up  the  supply  and  help  press  on  the  moving  mass. 

2.  Fractures  attending  the  movement — Crevasses. — Every  val- 
ley has  its  ridgy  sides,  its  sharp  turns,  its  abrupt  narrowings 
and  widenings,  its  irregular  bottom;  and  the  stiff  ice,  com- 
pelled  to  accommodate  itself -to  these  irregularities,  has,, 
consequently,  profound   crevasses  made   usually   along   its 
borders,  besides  multitudes  of  cracks  that  arc  not  visible  at 
the  surface ;  also,  still  profounder  chasms  when  wrenched 
in  turning  some  point;  longer  crevasses,  crossing  even  its 
whole  breadth,  when  the  ice  plunges  down  a  steep  place 
in  an  ice-cascade,  or  when,  on   escaping  from   a   narrow 
gorge,  it  moves  off    freely    again  with  increase  of  slope. 
Again,  it  may  lose  all  its  crevasses,  from  their  closing  up, 
when  the  motion  is  impeded  by  diminished  slope  or  other- 
wise. 

3.  Descent  below  the  snow-line. — The  icy  mass  thus  descends 
5000  to  7590  feet  below  the  snow-line,  or  the  limit  of  per- 
petual snow.    It  resists  the  melting  heat  of  summer  because 
of  its  mass,  just  like  the  ice  in  an  ice-house.     Though  start- 
ing where  all  is  white  and  barren,  it  passes  by  regions  of 
Alpine  flowers,  and  often  continues  down  to  a  country  of 
gardens  and  human  dwellings  before  its  course  is  finally  cut 
short  by  the  climate.     Thus,  the  Mer  de  Glace,  which,  under 
the  name  of  the  Bois  Glacier,  rises  in  Mont  Blanc  and  other 
neighboring  peaks,  terminates  in  the  vale  of  Chamouni. 
And  in  a  similar  manner  two  great  glaciers  descend  from 
the  Jungfrau  and  other  heights  of  the    Bernese  Alps   to 


GLACIERS. 


293 


the  plains  of  the  Grindelwald  valley  just  south  of  Inter, 
lachen. 

Fig.  367  represents  one  of  the  ice-streams  of  the  Mount 
Eosa  region  in  the  Alps,  from  a  view  in  Professor  Agassiz's 
work  on  Glaciers.     It  shows  the  lofty  regions  of  perpetual 
Fig.  367. 


Glacier  of  Zermatt,  or  the  Gorner  Glacier. 

snow  in  the  distance ;  the  bare  rocky  slopes  that  border  it, 
later  on  its  course ;  and  the  many  crevasses  that  intersect 
the  surface  of  the  ice-stream. 

4.  Glacier  torrent. — The  melting  over  the  surface  of  a 
glacier  and  about  the  sides  of  its  crevasses  gives  origin  to  a 
stream  of  water  flowing  beneath  it,  which  becomes  gradu- 
ally a  torrent  of  considerable  size,  and  finally  emerges  to 
the  light  from  beneath  the  bluff  of  ice  in  which  the  glacier 


294  DYNAMICAL   GEOLOGY. 

terminates.     Thence  it  continues  on  its  rocky  course  down 
the  valley. 

5.  Method  of  movement. — The  movement  and  condition  of 
a  glacier  is  almost  wholly  dependent  on  the  facility  with 
which  ice  breaks  and  unites  again  into  solid  ice  when  the 
broken  surfaces  are  brought  into  contact.    This  quality,  first 
noticed  by  Faraday  and  applied  to  Glaciers  by  Tyndall,  is 
called  regelation,  the  word  meaning  a  freezing  together  again. 
It  is  easily  tried  by  breaking  a  lump  of  ice  and  bringing  the 
surfaces  again  into   contact :  if  moist,  as  they  are  at  the 
ordinary  temperature,  they  at  once  become  firmly  united. 
A  glacier  moves  on  and  accommodates  itself  to  its  uneven 
bed  by  breaking  when  necessary,  and  in  its  progress  it  may 
soon  become  as  solid  as  before.     Thus  it  breaks  and  mends 
itself  as  it  goes. 

Small  portions  of  a  glacier  may  slide  along  its  bed,  but 
the  glacier  never  slides  as  a  whole.  In  some  places  there 
may  be  an  adaptation  to  an  uneven  surface  by  bending 
without  breaking  (which  may  take  place  if  the  force  be  ex- 
ceedingly slow  in  action) ;  but  this  also  is  a  means  of  motion 
of  small  importance,  compared  with  the  first  mentioned. 

6.  Transportation  by  Glaciers — Moraines. — Glaciers  become 
laden  with  stones  and  earth  falling  from  the  heights  above, 
or  coming  down  in  crushing  avalanches  of  snow  and  stones. 
The  stones  and  earth  make  a  band  along  either  border  of  a 
glacier,  and  such  a  band  is  called  a  moraine.     Yv~b.cn  two 
glaciers  unite,  or  a  tributary  glacier  joins  another,  they 
carry  forward  their  bands  of  stones  with  them ;  but  those 
on  the  uniting  sides  combine  to  make  one  moraine.    A  large 
glacier  like  that  in  fig.  367  may  have  many  moraines, — or 
one  less  than  the  number  of  its  tributaries.    Some  of  the 
masses  of  rock  on  glaciers  are  of  immense  size.      One  is 
mentioned  containing  over  200,000   cubic   feet, — which  is 
equivalent  in  cubic  contents  to  a  building  100  feet  long,  50 
wide,  and  40  high. 


GLACIERS.  295 

In  the  lower  part  of  a  glacier  the  several  moraines  lose 
their  distinctness  through  the  melting  of  the  ice;  for  this 
brings  to  one  level  the  dirt  and  stones  of  a  considerable  part 
of  its  former  thickness,  and  the  surface,  therefore,  becomes 
covered  throughout  with  earth  and  stones.  The  bluff  of  ice 
which  forms  the  foot  of  a  glacier  is  often  a  dirty  mass, 
showing  little  of  its  real  nature  in  the  distant  view. 

The  final  melting  leaves  all  the  earth  and  stones  in 
un stratified  heaps  or  deposits,  to  be  further  transported, 
eroded  and  arranged  by  the  stream  that  flows  from  the 
glacier. 

7.  Erosion  by  Glaciers. — A  glacier  so  laden  with  stones 
must  have  stones  in  its  lower  surface  and  sides  as  well  as 
in  its  mass.     As  it  moves  down  its  valley,  it  consequently 
abrades  the  exposed  rocks  over  which  it  passes,  smoothing 
and  polishing  some  surfaces,  covering  others  closely  with 
parallel  scratches,  and  often  ploughing  out  broad  and  deep 
channels,  besides  scratching  or  smoothing  the  ploughing 
boulders. 

In  addition  to  these  minor  operations,  glaciers  deepen  and 
widen  the  valleys  in  which  they  move.  In  this  work  they 
are  aided  by  the  frosts  (p.  290),  avalanches,  and  glacier 
torrents. 

8.  Glacier  regions. — The  best  known  of  Glacier  regions  are 
those  of  the  Alps,  in  one  of  which  Mont  Blanc  stands,  with 
its  summit  15,760  feet  above  the  sea.    There  are  glaciers  also 
in  the  Pyrenees  and  the  mountains  of  Norway,  Spitzbergen, 
in  the  Caucasus  and  Himalaya,  in  the  Southern  Andes,  in 
Greenland  and  other  Arctic  regions,  etc.     One  of  the  Spitz- 
bergen glaciers  borders  the  coast  for  11  miles  with  cliffs  of 
ice  100  to  400  feet  high.     The  great  Humboldt  Glacier  of 
Greenland,  north  of  79°  20',  has  a  breadth  at  foot  where  it 
enters  the  sea  of  45  miles;  and  this  is  but  one  glacier  among 
many  in  that  icy  land. 

26 


296  DYNAMICAL   GEOLOGY 


3.  ICEBERGS. 

When  a  glacier  like  those  of  Greenland  terminates  in  the 
sea,  the  icy  foot  bearing  its  moraines  becomes  broken  off 
from  time  to  time ;  and  these  fragments  of  glaciers,  floated 
away  by  the  sea,  are  icebergs.  The  geological  effects  of  ice- 
bergs have  been  stated  on  page  286. 

4.  FORMATION  OF  SEDIMENTARY  BEDS. 

The  following  is  a  brief  recapitulation  of  the  explanations 
of  the  origin  of  deposits  given  in  the  preceding  pages. 
Igneous  and  other  crystalline  rocks  are  not  here  included. 

1  Sources  of  material. — The  material  of  sedimentary 
rocks  has  come  either — (1)  from  the  degradation  of  pre- 
existing rocks,  or  (2)  from  a  state  of  solution  in  the  waters 
of  the  globe.  These  waters  have  in  general  taken  up  their 
mineral  material  originally  from  the  rocks,  except  that  part 
which  has  always  existed  in  the  ocean  ever  since  the  ocean 
began  to  be. 

The  principal  means  of  degradation  are  the  following : — 
1.  Erosion  by  moving  waters,  either  those  of  the  sea  or 
land  (pp.  283,  273) ;  2.  Erosion  by  ice,  cither  that  of  glaciers, 
icebergs,  or  ordinary  snow  and  ice  (pp.  291, 295);  3.  Pressure 
of  water  filtrating  into  fissures;  4.  Freezing  of  water  in 
fissures  (p.  290) ;  5.  Chemical  decomposition,  in  the  course 
of  which  rocks  are  crumbled  down  to  fragments  or  earth. 

2.  Formation  of  deposits. — The  methods  by  which  deposits 
have  been  formed  are  the  following : — 

1.  By  the  waters  of  the  sea. 

(1.)  Through  the  sweep  of  the  ocean  over  the  continents 
when  barely  or  partly  submerged, — making  (a)  sandy  or  pebbly 
deposits  near  or  at  the  surface  where  the  waves  strike,  or 
at  very  shallow  depths  where  swept  by  a  strong  current; 
(6)  argillaceous  or  shaly  deposits  near  or  at  the  surface, 


FORMATION  OF  SEDIMENTARY  BEDS.          297 

where  sheltered  from  the  waves,  and  also,  at  considerable 
depths,  out  of  material  washed  off  the  land  by  the  waves  or 
currents ;  but  not  making  (<•)  coarse  sandy  or  pebbly  deposits 
over  the  deep  bed  of  the  ocean,  as  even  great  rivers  carry- 
only  silt  to  the  sea ;  and  not  making  (d)  argillaceous  deposits 
over  the  ocean's  bed  except  along  the  borders  of  the  land, 
unless  by  the  aid  of  a  river  like  the  Amazon,  in  which  case, 
still,  the  detritus  is  mostly  thrown  back  on  the  coast  by  the 
waves  and  currents. 

(2.)  Through  the  waves  and  currents  of  the  ocean  acting 
on  the  borders  of  the  continent  with  the  same  results  as  above, 
except  that  the  beds  have  less  extent. 

(3.)  Through  living  species,  and  mainly  Mollusks,  Radiates, 
and  Rhizopods,  affording  calcareous  material  for  strata  (p. 
19),  and  Diatoms  and  some  Protozoans,  siliceous  material 
(p.  14).  All  rocks  made  of  corals,  and  the  shells  of  Mol- 
lusks, excepting  the  smallest,  require  the  help  of  the  waves 
at  least  to  fill  up  the  interstices;  but  Rhizopods  and  siliceous 
Infusoria  may  make  rocks  in  deep  water,  by  accumulation, 
which  are  in  no  sense  sedimentary.  See  pp.  265,  266. 

2.  By  the  waters  of  lakes. — Lacustrine  deposits  are  essen- 
tially like  those  of  the  ocean  in  mode  of  origin,  unless  the 
lakes  are  small,  when  they  arc  like  those  of  rivers. 

3.  By  the  running  waters  of  the  land. — (1.)  Filling  the  val- 
leys with  alluvium,  and  moving  the  earth  from  the  hills 
over  the  plains  (p.  277).      (2.)  Carrying  detritus  to  the  sea 
or  to  lakes,  to  make,  in  conjunction  with  the  action  of  the 
sea  or  lake  waters,  delta  and  other  seashore  accumulations 
(p.  279). 

4.  By  frozen  waters. — (1.)  Spreading  the  rocks  and  earth 
of  the  higher  lands  over  the  lower,  and,  in  the  process, 
bearing  onward  blocks  of  great  size,  such  as  cannot  be  moved 
by  other  means,  as  well  as  finer  material  (pp.  291,  294).    (2  ; 
Carrying  rocks  and  earth  from  the  land  to  the  ocean,  cither 
to  the  seashore,  making  accumulations  in  lines  or  moraines, 


298  DYNAMICAL   GEOLOGY. 

or  to  distant  parts  of  the  ocean,  as  from  the  Arctic  to  the 
Newfoundland  Banks;  and  thus  contributing  to  deep  or 
shallow  water  or  shore  sedimentary  accumulations,  distin- 
guished for  the  irregular  intermingling  of  huge  blocks  of 
stone,  pebbles,  and  earth  (p.  286). 

5.  GENERAL    EFFECTS    OF    EROSION   OVER   CON- 
TINENTS. 

The  outlining  of  mountain-ridges  and  valleys  has  been  in 
part  produced  by  subterranean  forces  upturning  and  frac- 
turing the  strata;  but  the  final  shaping  of  the  heights  is 
due  to  erosion.  This  cause  has  been  in  action  from  the  ear- 
liest time,  and  the  material  of  nearly  all  rocks  not  calcareous 
has  resulted  from  the  erosion  of  pre-existing  formations. 

The  Appalachians  have  probably  lost  by  denudation 
more  material  than  they  now  contain.  Mention  has 
been  made  of  faults  of  even  twenty  thousand  feet  along 
the  course  of  the  chain  from  Canada  to  Alabama.  In 
such  a  fault,  one  side  is  left  standing  twenty  thousand 
feet  above  the  other,  equivalent  in  height  to  some  of  the 
loftier  mountains  of  the  globe ;  and  yet  now  the  whole  is  so 
levelled  off  that  there  is  no  evidence  of  the  fault  in  the 
surface-features  of  the  country.  The  whole  Appalachian 
region  consists  of  ridges  of  strata  isolated  by  long  distances 
from  others  with  which  they  were  once  continuous.  Fig. 
253  represents  a  common  case  of  this  kind.  It  is  supposed 
by  some  geologists  that  the  Appalachian  and  Western  coal- 
fields were  once  united,  and  that,  in  western  Ohio  and  other 
parts  of  the  intermediate  region,  strata  thousands  of  feet 
deep,  from  the  Lower  Silurian  upward,  have  been  removed, 
and  this  over  a  surface  many  scores  of  thousands  of  square 
miles  in  area.  This  view  has  been  questioned  on  a  former 
page.  "Whether  true  or  not,  there  is  no  doubt  that  the 
anthracite  coal-fields  of  central  Pennsylvania  were  once  a 
part  of  the  great  bituminous  coal-field  of  western  Pennsyl- 


HEAT.  290 

vania  and  Virginia  (fig.  219,  p.  118).  They  are  now  in  iso- 
lated patches,  and  formations  of  great  extent  have  been 
removed  over  the  intervening  country.  The  Illinois  coal- 
region  is  broken  into  many  parts  in  consequence  of  similar 
denudation  and  uplifts. 

In  New  England  there  is  evidence  of  erosion  on  a  scale 
of  vast  magnitude  since  the  crystallization  of  its  rocks.  On 
the  summit-level  between  the  head-waters  of  the  Merrimac 
and  Connecticut,  there  are  several  pot-holes  in  hard  granite; 
one,  as  described  by  Professor  Hubbard,  is  ten  feet  deep  and 
eight  feet  in  diameter,  and  another  is  twelve  feet  deep.  They 
indicate  the  flow  of  a  torrent  for  a  long  age  where  now  it 
is  impossible;  and  the  period  may  not  be  earlier  than  the 
Post-tertiary.  Many  other  similar  cases  are  described  by 
Hitchcock. 

These  examples  of  denudation  are  sufficient  for  illustra- 
tion. Europe  and  the  other  continents  furnish  others  no 
less  remarkable,  and  to  an  indefinite  extent. 

IV.  HEAT. 

The  crust  of  the  earth  derives  heat  from  three  sources : — 
1.  The  sun,  an  external  source;  2.  The  earth's  heated  inte- 
rior; 3.  Chemical  and  mechanical  action.  The  first  two 
sources  are  geologically  the  most  important. 

Internal  heat. — The  fact  of  a  high  heat  in  the  earth's  inte- 
rior is  established  in  various  ways. 

1.  The  form  of  the  earth. — The  form  of  the  earth  is  a 
spheroid,  and  a  spheroid  of  just  the  shape  that  would  have 
resulted  from  the  earth's  revolution  on  its  axis,  provided  it 
had  passed  through  a  state  of  complete  fusion,  or  of  igneous 
fluidity,  and  had  slowly  cooled  over  its  exterior.  Hence 
follows  the  conclusion  that  it  has  passed  through  such  a 
state  of  fusion,  which  is  greatly  strengthened  by  the  other 
evidence  here  given.  Another  conclusion  also  follows: — 
namely,  that  the  earth's  axis  had  the  same  position  (or,  at 

26* 


300  DYNAMICAL   GEOLOGY. 

least,  very  nearly  the  same)  when  cooling  began  as  now. 
There  is  no  evidence  that  there  has  been  at  any  time  a 
change. 

2.  Crystalline  character  of  the  lowest  rocks. — On  descending 
through  the  earth's  strata,  the  lowest  reached  are  crystalline 
rocks.     The  Azoic  rocks,  which  are  the  earliest,  have  been 
found  to  be,  wherever  observed,  either  crystalline  or  firmly 
consolidated,  which  proves  that  they  must  have  been  sub- 
jected for  a  long  time  to  the  action  of  heat. 

3.  Artesian  borings. — In  deep  borings  for  water,  like  those 
mentioned  on  page  282,  it  has  been  found  that  the  tempera- 
ture of  the  earth's  crust  increases  one  degree  of  Fahrenheit 
for  every  50  or  60  feet  of  descent.     The  rate  of  1°  F.  for  50 
feet  of  descent,  in  the  latitude  of  New  York,  would  give 
heat  enough  to  boil  water  at  a  depth  of  8100  feet;  and  at  a 
depth  of  about  28  miles  the  temperature  would  be  3000°  F., 
or  that  of  the  fusing  point  of  iron.     Since,  however,  the 
fusing  temperature  of  any  substance   increases  with  the 
pressure,  the  depth  required  before  a  material   like  iron 
would  be  found  in  a  melted  state,  would  be  greater  than 
this.      The  facts  suffice  at  least  to  prove  that  the  earth  has 
a  source  of  heat  within,  and  that  a  very  high  heat  exists  at 
no  great  depth.     If  the  solid  crust  is  100  miles  thick,  it  is 
still  thin  compared  with  the  distance  to  the  earth's  centre. 

4.  Distribution  of  Volcanoes. — The  great  Pacific  Ocean  has 
nearly  a  complete  girt  of  volcanoes,  extinct  or  active,  and 
all  of  its  many  islands  that  are  not  coral  are  wholly  volcanic 
islands, — excepting  New  Zealand  and  a  few  others  of  large 
size  in  its  southwest  corner.     Volcanoes  occur  along  many 
parts  of  the  Andes  from  Tierra  del  Fuego  to  the  Isthmus  of 
Darien,  in  Central  America,  in  Mexico,  California,  Oregon, 
and  beyond;  in  the  Aleutian  Islands  on  the  north;  in  Kamt- 
chatka,  Japan,  the  Philippines,  New  Guinea.  New  Hebrides, 
New  Zealand  on  the  west;   and  on  Antarctic  lands  both 
Bouth  of  New  Zealand  and  South  America.     The  volcanio 


HEAT — VOLCANOES.  301 

region  thus  bounded  is  equal  to  a  whole  hemisphere,  and  is 
ample  proof  as  to  the  nature  of  the  whole  globe.  "With 
outlets  of  fire  so  extensively  distributed  over  this  vast  area, 
there  surely  must  be  some  universal  seat  of  fire  beneath. 

But  there  are  volcanoes  also  in  the  East  Indies  in  great 
numbers,  both  extinct  and  active,  in  the  islands  of  the  Indian 
Ocean,  in  the  "West  Indies,  in  the  islands  of  the  Atlantic, 
and  in  the  vicinity  of  the  Mediterranean  and  Red  Seas. 

The  various  evidences  mentioned  combine  to  prove  that 
the  interior  of  the  earth  is  a  source  of  heat. 

EFFECTS  OF  HEAT. 

The  following  are  the  effects  of  heat  here  considered : — 

1.  Volcanoes. 

2.  Igneous  ejections  that  are  not  volcanic. 

3.  Metamorphism,  and  the  production  of  mineral  veins. 

The  heat  of  the  globe  is  also  one  of  the  causes  of  earth- 
quakes, of  change  of  level  in  the  earth's  crust,  and  of  the 
elevation  of  mountains :  these  subjects  are  considered  in 
the  following  chapter.  It  is  an  important  agent  also  in  all 
chemical  changes. 

1.  VOLCANOES. 

A.  General  nature  of  volcanoes  and  their  products. 
Volcanoes  are  mountain-elevations  of  a  somewhat  conical 
form,  which  eject  or  have  ejected  at  some  time  streams  of 
melted  rock.  If  the  fire-mountain  has  at  present  no  active 
fires  within,  and  is  emitting  no  vapors,  it  is  said  to  be 
extinct.  The  following  figure  is  a  sketch  of  the  lofty  volcano 
of  Cotopaxi,  as  published  by  Humboldt.  The  height  of  the 
peak  is  18,876  feet.  The  larger  volcanic  mountains  are 
seldom  so  steep  as  in  this  figure.  Etna,  about  10,000  feet 
high,  and  Mount  Kea  and  Mount  Loa  of  Hawaii,  nearly 
14*000  feet,  have  an  average  slope  of  less  than  10  degrees. 
The  form  of  a  cone  with  a  slope  of  7  degrees— which  is  the 


302 


DYNAMICAL   GEOLOGY. 


average  for  the  Hawaian  volcanoes — is  shown  in  figs.  369, 
370 ;  fig.  369  has  a  pointed  top,  like  Mount  Kea,  and  fig.  370 


Volcano  of  Cotopaxi. 

a  rounded  outline,  like  Mount  Loa,  whose  form  is  that  of  a 
very  low  dome 

Fig.  369. 


Fig.  370. 


The  highest  of  volcanic  mountains  on  the  globe  are  the 
Aconcagua  peak  in  Chili,  23,000  feet,  and  Sorata  and  Illi- 
mani,  in  Bolivia,  each  over  24,000  feet.  The  former  appears 
to  be  still  emitting  vapors,  showing  that  the  fires  are  not 
wholly  extinct.  The  mountains  Shasta,  Hood,  Helens,  and 


HEAT — VOLCANOES.  303 

others  in  California  and  Oregon  are  isolated  volcanic  cones 
13,000  to  15,000  feet  high. 

The  cavity  or  pit  in  the  top  of  a  volcanic  mountain, 
where  the  lavas  may  often  be  seen  in  fusion,  is  called  the 
crater.  It  is  sometimes  thousands  of  feet  deep,  but  may  be 
quite  shallow;  and  in  extinct  volcanoes  it  is  often  wholly 
wanting,  owing  to  its  having  been  left  filled  when  the  fires 
went  out. 

The  liquid  rock  issuing  from  a  crater,  and  the  same  after 
becoming  cold  and  solid,  is  called  lava. 

An  active  crater,  even  in  its  most  quiet  state,  emits  vapors. 
These  vapors  are  mostly  simple  steam,  or  aqueous  vapor; 
but  in  addition  there  are  usually  sulphur  gases,  and  some- 
times carbonic  acid  or  muriatic  acid. 

In  a  time  of  special  activity,  fiery  jets  are  sometimes 
thrown  up  to  a  great  height,  which,  in  the  distance,  at  night 
look  like  a  discharge  of  sparks  from  a  furnace.  These  jets 
are  made  of  red-hot  fragments  of  the  liquid  lava ;  the  frag- 
ments cool  as  they  descend  about  the  sides  of  the  crater,  and 
are  then  called  cinders. 

When  a  shower  of  rain,  or  of  moisture  from  the  condensed 
steam,  accompanies  the  fall  of  the  cinders,  the  result  is  a 
mud-like  mass,  which  dries  and  becomes  a  brownish  or  yel- 
lowish-brown layer  or  stratum  called  tufa.  It  is  often  much 
like  a  soft  coarse  sandstone,  only  the  materials  are  of  vol- 
canic origin. 

The  materials  produced  by  the  volcano  arc.  then — 1. 
Lavas;  2.  Cinders;  3.  Tufas;  4.  Vapors  or  Gases,  which  are 
mostly  vapor  of  water,  partly  sulphur  gases,  and  in  some  cases 
also  carbonic  acid,  muriatic  acid,  and  some  other  materials. 

The  lavas  are  of  various  kinds.  They  are  more  or  less 
cellular;  sometimes  light  cellular,  like  the  scoria  of  a  furnace; 
but  more  commonly  heavy  rocks  with  some  scattered  ragged 
cellules  or  cavities  through  the  mass.  A  stream  of  lava  in 
a  crater,  of  cnis  more  solid  kind,  has  often  a  few  inches  of 


304  DYNAMICAL   GEOLOGY. 

scoria  at  top, — as  a  running  stream  of  syrup  may  have  its 
scum  or  froth.  The  most  of  the  scoria  has  this  scum-like 
origin.  Pumice  is  a  very  light  grayish  scoria,  full  of  long 
and  slender  parallel  air-cells. 

The  lavas  may  be  black  or  brownish,  and  greenish-black, 
in  color,  and  very  heavy  (specific  gravity  above  2.9),  as  the 
Dolerite  and  Basalt,  described  on  page  26 ;  or  they  may  be 
rather  light  (specific  gravity  under  2.7)  and  grayish  in  color, 
as  trachyte  and  phonolite.  Phonolite  is  a  very  compact  felds- 
pathic  rock,  giving  a  clinking  sound  under  the  hammer. 

A  volcanic  mountain  is  made  out  of  the  ejected  materials; 
cither — (1)  out  of  lavas  alone;  or  (2)  of  cinders  alone;  or 
(3)  of  tufas  alone;  or  (4)  of  alternations  of  two  or  more 
of  these  ingredients.  As  the  centre  of  the  mountain  is  the 
centre  of  the  active  fires,  the  ejections  flow  off  or  fall  around 
it,  and  hence  the  form  of  a  volcanic  peak  necessarily  tends 
to  become  conical. 

The  average  angle  of  slope  of  a  lava-cone  is  from  3°  to  10° ; 
of  a  tufa-cone,  15°  to  30° ;  of  a  cinder-cone,  30°  to  45° ;  of 
mixed  cones,  intermediate  inclinations  according  to  their 
constitution. 

B.  Volcanic  eruptions. 

The  process  of  eruption,  though  the  same  in  general 
method  in  all  volcanoes,  varies  much  in  its  phenomena. 
The  fundamental  principles  are  well  shown  at  the  great 
craters  of  Hawaii,  the  southeasternmost  of  the  Hawaian 
(or  Sandwich)  Islands. 

1.  Hawaian  Volcanoes. — 1.  General  description. — Hawaii  is 
made  up  mail  v  of  three  volcanic  mountains, — two,  Mount 
Loa  and  Mou^t  Kea,  nearly  14,000  feet  high;  and  one  (the 
western),  Moui.t  Hualalai,  about  10,000  feet.  Mount  Kea 
is  alone  in  being  extinct.  The  average  slopes  of  the  two 
highest  are  well  shown  in  figs.  369,  370,  on  page  302,  fig. 
369  representing  Mount  Kea  and  370  Mount  Loa. 

Mount  Loa  has  a  great  crater  at  top,  and  another  4000 


HEAT — VOLCANOES. 


305 


feet  above  the  level  of  the  sea  (at  k,  fig.  370).  The  latter  is 
the  famous  one  called  Kilauea,  and  also  Lua  Pde  or  Pele's 
pit,  Pele  being,  in  the  mythology  of  the  Hawaians,  the 
goddess  of  the  volcano. 

The  accompanying  map  of  the  southeastern  portion  of 
Fig.  371. 


Map  of  part  of  Hawaii. 

Hawaii  shows  the  positions  of  Mount  Loa  and  Mount  Kea, 
and  of  the  crater  of  Kilauea,  besides  other  craters  at  the 
summit  of  Mount  Loa,  and  on  the  sides  at  P,  A,  B,  C,  K,  &c. 
2.  Kilauea. — The  crater  of  Kilauea  is  literally  a  pit.  It 
is  three  miles  in  greatest  length,  and  nearly  two  in  greatest 
breadth,  and  about  seven  and  a  half  miles  in  circuit.  It  is 
large  enough  to  contain  Boston  proper  to  South  Bridge, 
three  times  over,  or  to  accommodate  400  such  structures  as 
St.  Peter's  at  Eome.  The  pit  has  nearly  vertical  sides  of 
solid  rock  (made  of  lavas  piled  up  in  successive  layers),  and 
is  1000  feet  in  depth  after  its  eruptions,  and  600  when  most 
filled  with  lavas  (its  present  condition).  The  bottom  is  a 


306  DYNAMICAL   GEOLOGY. 

great  area  of  solid  lava ;  and  it  may  be  surveyed  from  the 
brink  of  the  pit,  even  when  in  most  violent  action,  as  calmly 
and  safely  as  if  the  landscape  were  one  of  houses  and 
gardens.  In  some  parts  of  it  there  are  ordinarily  one  or 
more  lakes  or  pools  of  liquid  lava,  and  from  these  and 
other  points  vapors  rise.  The  largest  lake  is  sometimes 
1000  feet  or  more  in  diameter. 

3.  Action  in  Kilauea. — The  action  is   simply  this.     The 
lavas  in  the  active  pools  are  in  a  state  of  ebullition,  jets 
rising  and  falling  as  in  a  pot  of  boiling  water,  with  this  dif- 
ference, that  the  jets  are  30  or  40  feet  high.     Such  jets,  in 
lava  as  well  as  water,  arise  from  the  effort  of  vapors  to 
escape ;  in  vrater  the  vapor  is  steam  derived  from  the  water 
itself;  in  lavas  it  is  steam  and  other  gases  from  materials  in 
the  lavas. 

The  lavas  of  the  pools  or  lakes  overflow  at  times  and 
spread  in  streams  across  the  great  plain  that  forms  the 
bottom  of  the  crater.  In  times  of  great  activity  the  pools 
and  lakes  are  numerous,  the  ebullition  incessant,  and  the 
overflowings  follow  one  another  in  quick  succession. 

4.  Cause  of  eruption. — By  these  overflows  the  pit  slowly 
fills,  and  in  the  course  of  a  few  years  the  bottom  is,  conse- 
quently, 400  feet  above  its  lowest  level ;  so  that  the  depth 
is  thus  reduced  from  1000  to  600  feet.     This  addition  of  400 
feet  increases  400  feet  the  height  of  the  central  column  of 
liquid  lava  of  the  crater,  and  causes  a  corresponding  increase 
of  pressure  against  the  sides  of  the  mountain.    The  amount 
of  this  pressure  is  at  least  two  and  a  half  times  as  great  as 
that  which  an  equal  column  of  water  would  produce.     The 
mountain  should  be  strong  to  bear  it.     The  lavas  at  such 
times  may  be  in  a  state  of  violent  activity,  and  when  so 
there  is  an  addition  to  the  pressure  against  the  sides  of  the 
mountain,  arising  from  the  force  of  the  imprisoned  vapors. 

The  consequence  of  this  increase  of  pressure,  both  from 
the  lavas  and  the  augmented  vapors,  may  be,  and  has  several 


HEAT — VOLCANOES.  307 

times  been,  a  breaking  of  the  sides  of  the  mountain.  One 
or  more  fractures  result,  and  out  flows  the  lava  through 
the  openings.  Thus  simple  are  the  eruptions  of  the  Hawaian 
volcanoes. 

In  one  such  eruption  the  lavas  first  appeared  at  the 
surface  a  few  miles  below  Kilauea  (at  P,  fig.  371),  and  then 
again  at  other  points  more  remote,  A,  B,  C,  m;  and  finally 
a  stream  began  at  n,  a  point  20  miles  from  the  sea,  which 
continued  to  the  shores  at  Nanawale.  Here,  on  encounter- 
ing the  waters,  the  great  flood  of  lava  was  shivered  into 
fragments,  and  the  whole  heavens  were  thick  with  an  illu- 
minated cloud  of  vapors  and  cinders,  the  light  coming  from 
the  fiery  stream  below. 

This  eruption  of  Kilauea  took  place,  it  Trill  be  observed, 
not  over  the  sides  of  the  crater,  but  through  breaks  in  the 
mountain's  sides  below;  and  the  pressure  of  the  column  of 
lava  within,  along  with  the  pressure  of  the  escaping  vapors, 
appear  to  have  caused  the  break.  In  all  known  eruptions 
of  Kilauea  the  process  has  been  that  described. 

5.  Summit-crater  of  Mount  Loa. — Eruptions  have  also  taken 
place  within  a  few  years  from  the  summit-crater  of  the  same 
mountain  (Mount  Loa),  or  at  a  point  nearly  14,000  feet  high 
above  the  sea;  and  in  each  case  there  has  been, not  an  over- 
flow from  the  crater,  but  an  outflow  through  breaks  in  the 
sides  of  the  mountain.     In  one  case  there  was  first  a  small 
issue  of  lavas  near  the  summit,  and  then  another  of  great  mag- 
nitude about  10,000  feet  above  the  sea-level.    At  this  second 
outbreak  the  lava  was  thrown  up  in  a  fountain,  or  mass  of 
jets,  several  hundred  feet  high;  and  thus  it  continued  in 
action  for  several  days.    The  forms  of  the  fountain  of  liquid 
fire  were  compared  by  Eev.  Mr.  Coan  to  the  clustered  spires 
of  some  ancient  Gothic  cathedral. 

6.  Cause  of  the  jet  or  fountain  of  lava. — The  pressure  pro- 
ducing this  jet  was  that  of  the  column  of  lava  between  the 
point  of  outbreak  and  the  lex»el  of  the  lavas  in  the  summit- 

27 


308  DYNAMICAL   GEOLOGY. 

crater  3000  to  4000  feet  above.  The  same  pressure  in  con- 
nection with  confined  vapors  must  have  caused  the  breaking 
of  the  mountain  in  which  the  eruption  began.  There  have 
been  no  great  earthquakes  accompanying  the  Hawaian  erup- 
tions, sometimes  not  even  slight  ones,  the  first  announce- 
ment being  merely  "a  light  on  the  mountain."  Moreover, 
when  the  summit-crater  has  been  thus  active,  Kilauea, 
though  10,000  feet  lower  on  the  same  mountain  and  even  a 
larger  pit-crater,  has  shown  no  agitation  and  no  signs  what- 
ever of  sympathy. 

7-  Conclusions. — These  cases  of  eruption  indicate — (1)  that 
the  lavas  go  on  gradually  increasing  the  pressure  in  the 
interior  by  their  accumulation  and  rising  to  a  higher  level ; 
and  that  finally,  when  the  mountain  can  no  longer  resist  it, 
it  breaks  and  lets  the  heavy  liquid  out.  They  show  (2)  that 
while  earthquakes  may  attend  volcanic  action,  they  are  no 
necessary  part  of  it.  They  show  (3)  that  lavas  may  be  so 
very  liquid  that  no  cinders  are  formed  during  a  great  erup- 
tion. For  in  the  ebullition  of  the  lava  in  the  boiling  lakes 
of  Kilauea,  the  jets  (made  by  the  confined  vapors)  are  thrown 
only  to  a  height  of  30  or  40  feet ;  and  on  falling  back,  the 
material  is  still  hot  and  does  not  become  cooled  fragments ; 
it  either  falls  back  into  the  pool  or  lake,  or  becomes  plastered 
to  its  sides. 

At  some  of  the  eruptions  of  Mount  Loa  the  lava  has  con- 
tinued down  the  mountain  to  a  distance  of  30  or  40  miles. 

2.  Vesuvius. — Vesuvius  is  an  example  of  another  type  of 
volcano.  The  lavas  are  so  dense  or  viscid  that  jets  cannot 
rise  freely  over  the  surface :  the  vapors  are  kept  confined 
until  they  form  a  bubble  of  great  dimensions ;  and  when  such 
a  bubble,  or  a  collection  of  them,  bursts,  the  fragments  are 
sometimes  thrown  thousands  of  feet  in  height.  The  crater, 
at  a  time  of  eruption,  is  a  scene  of  violent  activity,  and  can- 
not be  approached  Destructive  earthquakes  often  attend 
the  eruptions. 


HEAT — VOLCANOES.  309 

The  lavas  at  Vesuvius  may  flow  directly  from  the  top  of 
the  crater;  but  they  generally  escape  partly,  if  not  entirely, 
through  fissures  in  the  sides  of  the  mountain. 

3.  Comparison  of  Mount  Loa  and  Vesuvius  as  to  causes  of 
eruption  and  nature  of  the  mountains. — Of  the  two  causes  of 
eruption — hydrostatic  pressure  and  elastic  force  of  confined 
vapors — the  latter  may  be  the  most  effective  at  Vesuvius, 
while  the  former  is  so  at  Hawaii.     Mount  Loa  on  Hawaii  is 
an  example  of  the  great  free-flowing  volcanoes  of  the  world, 
and  the  mountain  is  almost  wholly  a  lava-cone.    Vesuvius  is 
an  example  of  a  smaller  vent  with  less  liquid  lavas;  and  the 
cone  is  made  up  of  both  solid  lavas  and  cinders. 

4.  Lateral  cones  of  volcanoes. — In  eruptions  through  fissures 
the  lavas  may  continue  issuing   for  some  days  or  weeks 
through  the  more  open  or  widest  part  of  the  fissure,  and 
consequently  form  at  this  point  a  cone  of  cinders  or  lavas. 
Thus  have  originated  innumerable  cones  on  the  slopes  of 
Etna  and  other  volcanic  mountains. 

5.  Submarine   eruptions. — The   eruptions   may   sometimes 
take  place  from  the  submarine  slopes  of  the  mountain  when 
it  is  situated  near  the  sea,  as  has  happened  with  Etna  and 
Mount  Loa;  and  in  such  cases  cones  of  fragmental  lavas  or 
solid  layers  may  form  under  water  about  the  opened  vent. 
Fishes  and  other  marine  animals  are  usually  destroyed  in 
great  numbers  by  such  submarine  eruptions. 

C.  Subsidences  of  volcanic  regions— Overwhelming  of  cities. 
— Among  the  attendant  effects  of  volcanoes  are  the  sinking 
oT  regions  in  their  vicinity  that  have  been  undermined  by 
the  outflow  of  the  lavas,  and  the  tumbling  in  of  the  summit 
of  a  mountain.  Another  is  the  burial,  not  only  of  fields 
and  forests,  but  even  of  cities  and  their  inhabitants,  by  the 
outflowing  streams,  or  the  falling  cinders  and  accumulating 
tufas.  Pompeii  and  Herculaneum  are  two  of  the  cities  that 
have  been  buried  by  Vesuvius;  and  every  few  j-ears  we 


310  DYNAMICAL   GEOLOGY. 

hear  of  some  new  devastations  made  on  habitations  or  farms 
by  this  uneasy  volcano. 

C.  Subordinate  volcanic  phenomena. 

1.  Solfataras. — In  the  vicinity  of  volcanoes,  and  sometimes 
in  regions  in  which  no  volcanoes  exist,  there  are  areas  where 
steam,  sulphur  vapors,  and  perhaps  carbonic  acid  and  other 
gases,  are  constantly  escaping.     Such  areas  are  called  sol- 
fataras.     The  sulphur  gases  deposit  sulphur  in  crystals  or 
incrustations  about  the  fumaroles  (as  the  steam-holes  are 
called);  and  alum  and  gypsum  often  form  from  the  action 
of  sulphuric  acid  (another  result  from  the  sulphur  gases)  on 
the  rocks. 

Fountains  or  springs  of  hot  waters  are  common  in  such 
places,  and  arc  often  so  abundant  as  to  be  used  for  baths. 

2.  Geysers. — In  Iceland  at  the  Geysers  the  heated  waters 
are  thrown  out  in  intermittent  jets  in  some  cases  to  a  height 
of  200  feet.    Subterranean  streams  arising  in  the  mountains 
are  supposed  to  pass  over  heated  rocks,  and  then  to  be  forced 
upward  by  the  vapors  produced  by  the  heat.     Such  heated 
waters  act  on  the  rocks,  decomposing  them,  and  thereby 
become  slightly  alkaline  and  also  siliceous  solutions.      The 
silica  thus  taken  into  solution  is  deposited  again  around  the 
Geysers  in  many  beautiful  forms,  besides  making  the  bowl 
of  the  cavity  or  basin  from  which  the  waters  are  thrown 
out,  and  forming  numerous  petrifactions. 

"When  the  basin  of  a  boiling   pool  consists  of  earth  or 
mud,  mud-cones  arc  formed,  as  in  California. 

2.  IGNEOUS  ERUPTIONS  NOT  VOLCANIC. 
It  has  been  stated  that  eruptions  of  volcanoes  generally 
take  place  through  fissures.  Fissures  have  often  been  made 
in  the  earth's  crust  and  filled  with  liquid  rock,  also,  in 
regions  remote  from  volcanoes.  Such  fractures  of  the  crust 
of  the  earth  must  have  descended  to  some  seat  of  fires,  if 


NON-VOLCANIC    IGNEOUS    ERUPTIONS  311 

not  through  to  the  earth's  liquid  interior.  Whatever  cause 
was  sufficient  to  break  through  the  crust  would  have  sufficed 
to  press  out  the  liquid  rock  beneath.  The  narrow  mass  of 
igneous  rock  which  fills  such  fissures  is  called  a  dike  (p.  30). 
The  igneous  rock  is  generally  without  cellules  or  air-cavities; 
or,  if  present,  they  are  neatly  formed,  and  not  ragged  like 
those  of  lavas.  Such  rocks  having  the  cavities  filled  with 
minerals  (as  quartz,  zeolites,  etc.)  are  called  Amygdaloids. 

The  most  common  rocks  of  such  dikes  are  dolerite  and 
basalt  (p.  26),  and  next  to  these,  diorite  and  porphyry.  The 
dolerite,  basalt,  and  diorite  are  often  called  trap. 

Dikes  of  rocks  of  this  kind  are  mentioned  and  described 
on  p.  165  as  occurring  in  various  parts  of  the  Eastern  border 
region  of  North  America, — constituting  the  Palisades  on  the 
Hudson;  Bergen  Hill  and  other  heights  in  New  Jersey; 
many  bold  bluffs  in  Connecticut  between  New  Haven  and 
its  northern  boundary;  Mount  Tom  and  Mount  Holyoke 
and  other  elevations  in  central  Massachusetts,  and  ridges  in 
Nova  Scotia  near  the  Bay  of  Fundy.  The  rocks  of  the 
Salisbury  Craigs  near  Edinburgh,  and  of  the  Giants'  Cause- 
Fig.  372. 


Basaltic  columns,  coast  of  Illawana,  New  South  Wales. 


way  and   Fingal's  Cave,  are  other   examples.      They  are 
common  on  all  the   continents,  especially  in  the  regions 


312  DYNAMICAL   GEOLOGY. 

between  the  summits  of  the  border  mountains  and  the 
ocean,  which  are  usually  between  300  and  700  miles  in 
breadth ;  as,  for  example,  between  the  Appalachians  and  the 
Atlantic,  and  between  the  Rocky  ^Mountains  and  the  Pacific. 
These  basaltic  and  dolcritic  rocks  are  often  columnar  in 
their  forms,  as  illustrated  in  the  preceding  sketch  of  a  scene 
in  New  South  AValcs.  The  Giants'  Causeway  is  remarkable 
for  the  regularity  of  its  columns.  Similar  scenes  of  great 
beauty  occur  on  Lake  Superior,  and  some  of  less  perfection 
in  the  Connecticut  River  valley  and  the  Palisades  on  the 
Hudson.  These  columns  were  formed  when  the  rock  cooled, 
and  are  due  partly  to  contraction  and  partly  to  a  concre- 
tionary structure  produced  in  the  process  of  cooling.  The 
size  of  the  concretions  in  such  a  case  determines  the  diame- 
ter of  the  columns,  and  depends  on  the  amount  of  material 
and  the  rate  of  cooling,  the  size  being  larger  the  slower  the 
rate. 

3.   METAMORPHISM. 

1.  Nature  of  met  amor phism. — The  term  metamorphism  sig- 
nifies change  or  alteration ;  and  in  Geology,  a  change  in  the 
earth's  rocks  or  strata,  under  the  influence  of  heat  below 
fusion,  resulting  in  crystallization,  or,  at  least,  firm  solidifi- 
cation :  as  when  argillaceous  shale  is  altered  to  roofing-slate 
or  mica  schist;  argillaceous  sandstone,  to  gneiss  or  granite; 
common  compact  limestone,  to  granular  limestone  or  statuary 
marble;  a  common  siliceous  sandstone,  to  a  hard  grit  or  to 
quartzite.  The  more  common  kinds  of  rocks  resulting  through 
metamorphism  are  described  on  pages  23,  24. 

2.  Effects. — The  effects  of  metamorphism  include  not  only 
— (1)  solidification  and  (2)  crystallization,  but  also — 

(3.)  A  change  of  color ;  as  the  gray  and  black  of  common 
limestone  to  the  white  color  or  the  clouded  shadings  of 
marble ;  and  the  brown  and  yellowish-brown  of  some  sand- 
stones colored  by  iron,  to  red,  making  red  sandstone  and 
jasper-rock. 


METAMORPHI8M  313 

(4.)  In  most  cases,  a  partial  or  complete  expulsion  of 
water,  but  not  in  all ;  for  serpentine,  a  metamorphic  rock, 
is  one-eighth  (or  13  per  cent.)  water. 

(5.)  A  partial  or  complete  loss  of  bitumen,  if  this  ingre- 
dient be  present;  as  when  bituminous  coal  is  changed  to 
anthracite  or  graphite  (pp.  76,  160). 

(6.)  An  obliteration  of  all  fossils ;  or  of  nearly  all  if  the 
metamorphism  is  partial. 

(7.)  In  many  cases,  a  change  of  constitution ;  for  the  ingre- 
dients subjected  to  the  metamorphic  process  often  enter 
into  new  combinations :  as  when  a  limestone,  with  its  impu- 
rities of  clay,  sand,  phosphates,  and  fluorids,  gives  rise  under 
the  action  of  heat  not  merely  to  white  granular  limestone, 
but  to  various  crystalline  minerals  disseminated  through 
it,  such  as  mica,  feldspar,  scapolite,  pyroxene,  etc. ;  or  when 
an  argillaceous  sandstone  becomes  a  gneiss  or  schist  full  of 
garnets,  tourmaline,  hornblende,  etc. 

Thus  metamorphism  often  fills  a  rock  with  crystals  of 
various  minerals.  Even  the  gems  are  among  its  results;  for 
topaz,  sapphire,  emerald,  and  diamond  have  been  produced 
through  metamorphic  action.  What  is  of  more  value,  this 
process  makes  out  of  rude  shales  and  sandstones  hard  and 
beautiful  crystalline  rocks,  as  granite  and  marble,  for  archi- 
tectural and  other  purposes.  Man's  imitations  of  nature  in 
this  line  are  seen  in  his  little  red  bricks. 

3.  Process. —  Water  and  heat  are  two  agencies  essential  in 
metamorphism. 

Metamorphism  has  taken  place  generally  when  the  rocks 
were  undergoing  great  disturbances  or  uplifts,  foldings  and 
faultings,  and,  therefore,  when  the  conditions  were  favor- 
able for  the  escape  of  portions  of  the  earth's  internal  heat. 
This  heat  has  penetrated  the  wet  rocks.  The  water  or 
moistm-e  within  the  rocks  has  rendered  them  good  con- 
ductors of  heat,  and  has  aided  directly  in  conveying  the 
heat.  Moreover,  where  the  heat  was  above  212°  F.,  or  the 


314  DYNAMICAL   GEOLOGY. 

boiling  point  of  water, — as  it  probably  has  been  in  most 
cases  of  metamorphic  change, — all  of  it  bas  passed  to  what 
is  called  a.  superheated  state;  and  in  this  state  it  has  great 
power  in  dissolving  and  decomposing  minerals  and  pro- 
moting new  combinations  and  crystallizations.  Under  such 
circumstances,  the  moisture  becomes  itself  a  solution  by 
taking  up  mineral  substances  from  the  rock  in  which  it  is  at 
the  time;  and  these  added  materials  are  the  source  of  a 
large  part  of  its  power  in  making  changes;  for  if  it  thus 
becomes  an  alkaline  siliceous  solution,  like  the  waters  of 
the  Geysers  (see  p.  310),  it  may  not  only  deposit  quartz  in 
all  seams  or  cavities,  if  the  temperature  favors  this,  but  it 
may,  under  other  favorable  circumstances,  help  in  making 
feldspars,  micas,  and  many  other  alkaline  siliceous  minerals; 
or  if  the  alkalies  are  mostly  absent  and  iron  is  present,  the 
siliceous  waters  may  promote  the  crystallization  of  stauro- 
tide  and  hornblende. 

The  change  of  a  siliceous  sandstone  to  a  grit  or  quartzito 
requires  nothing  but  these  conditions;  for  the  moisture  in 
such  a  rock  would  become,  when  subjected  to  slow  heating, 
siliceous,  from  the  material  of  the  sandstone,  and  the  silica 
taken  up  would  be  deposited  again  as  the  rock  cooled,  and 
so  cement  and  solidify  the  whole  into  a  true  quartzite.  Such 
quartzites  often  contain  some  feldspar,  a  mineral  that  would 
also  be  formed  if  a  little  alkali  and  alumina  were  present. 

These  are  examples  of  the  various  ways  in  which  heated 
and  superheated  waters  may  promote  metamorphic  changes. 
Direct  experiments  have  shown  that  these  kinds  of  crystal- 
lizations do  result  from  the  action  of  heat. 

Pressure  is  requisite  for  most  metamorphic  changes. 
Limestone  heated  without  pressure  loses  its  carbonic  acid 
and  becomes  quick-lime,  as  in  a  lime-kiln;  but  if  under 
pressure,  the  carbonic  acid  is  not  driven  off.  The  possibility 
of  the  crystallization  of  limestone  by  heat,  under  pressure, 
has  been  proved  by  direct  experiment.  The  necessary 


METAMORPHISM.  315 

pressure  may  be  that  of  an  ocean  above;  or  it  may  be  only 
that  of  the  superincumbent  rocks,  a  few  hundred  feet  of 
which  Avould  be  quite  sufficient. 

Tho  similarity  of  argillaceous  sandstones  to  gneiss  or 
granite  is  often  much  greater  than  appears  to  the  eye. 
They  have  been  made  by  the  wear  of  just  such  rocks  as 
gneiss  and  granite ;  and  the  sand  of  the  former  is  the  quartz 
of  the  latter,  the  clay  of  the  former  frequently  only  the 
pulverized  feldspar  of  the  latter,  and  mica  may  be  in  grains 
in  the  former  as  it  is  in  the  latter  :  so  that  the  change 
would  in  such  a  case  be  mainly  a  change  in  the  state  of 
crystallization.  By  heating  a  bar  of  steel  to  a  temperature 
far  short  of  fusion,  and  cooling  it  again,  it  may  be  made 
coarse  or  fine  steel,  the  process  changing  the  grains  by 
causing  many  small  grains  to  combine  to  make  the  large 
ones  in  the  coarser  kind  and  the  reverse  for  the  finer  kind. 
There  is  something  analogous  in  the  change  of  an  argil- 
laceous sandstone  to  a  gneiss  or  granite  above  described. 

If  the  sandstone  or  shale  contains  little  or  no  alkali,  its 
metamorphism  cannot  produce  a  gneiss  or  mica  slate,  since 
feldspar,  one  of  the  constituents  of  these  rocks,  contains  an 
alkali  as -an  essential  ingredient.  The  result  will  necessarily 
vary  with  the  constituents  of  the  original  rock,  and  tho 
heat  and  other  conditions  attending  the  metamorphism. 

Often,  however,  the  material  derived  from  the  wear  of 
gneiss  and  granite  and  other  rocks  is  not  only  pulverized, 
but  also  more  or  less  decomposed : — the  feldspar,  for 
example,  undergoes  a  change  in  its  alkalies,  or  loses 
them  altogether,  they  being  carried  off  by  waters,  or  the 
mica  may  lose  its  oxyd  of  iron  and  alkalies;  or  waters 
may  bring  in  oxyd  of  iron  or  other  ingredients ;  and  so  on  : 
und  in  such  a  case  the  process  of  metamorphism  could 
not,  of  course,  restore  the  original  rock.  The  new  rock 
made  would  contain  no  feldspar  if  the  alkalies  had  been 
removed ;  but  it  might  be  an  argillite,  or,  if  much  oxyd  of 


316  DYNAMICAL   GEOLOGY. 

iron  were  present,  a  hornblende  rock,  or  some  other  kind, 
according  to  the  nature  of  the  material  subjected  to  the 
change,  and  the  amount  or  continuance  of  the  heat. 

Examples  of  the  metamorphism  of  extensive  regions  of 
the  earth  have  already  been  mentioned  on  pages  75,  156, 
and  these  pages  should  here  be  perused  anew.  In  the  case 
of  the  Azoic  formation,  the  rocks  of  a  large  part  of  the 
earth's  surface  may  have  been  in  process  of  crystallization 
at  one  time;  and  in  that  of  the  Appalachian  chain  changes 
of  this  kind  took  place  not  only  over  the  region  from  Labra- 
dor to  Alabama,  but  simultaneously  in  Europe  and  probably 
<m  the  other  continents. 

4.   FORMATION  OF  VEINS. 

1.  Nature  and  origin  of  spaces   occupied  by  veins. — Veins 
occupy  (1)  the  cracks  and  fissures  made  in  rocks  and  (2) 
openings  between  their  layers, especially  those  of  schistose 
or  slaty  kinds.     They  are  produced  in  great  numbers  when 
a  region  of  rocks  is  undergoing  uplift,  or  when  a  folding 
of  the  strata  is  in  progress.     The  fractures  may  descend 
through  the  crust,  or  to  regions  of  melted  rock,  as  in  the 
case  of  the  formation  of  dikes  (p.  310) ;  they  may  descend 
to   depths  of  intense   heat  without   reaching  liquid   rock 
below;  they  may  intersect  either  several  strata  lying  to- 
gether, or  only  one  of  a  series,  for  some  rocks  will  become 
fractured  by  the  same  circumstances  that  will  leave  others 
unbroken. 

2.  Filling  of  veins. — Whatever  the  cause  of  the  fractures, 
the  causes   that  produce   so   great   metamorphic   changes 
would  fill  the  fissures  and  openings  (when  not  so  deep  as  to 
reach  to  regions  of  liquid  rock)  with  minerals  from  the  rock 
either  side  of  the  fissure.     The  heated  waters,  or  moisture, 
of  the  rocks  would  slowly  fill  all  cavities.     A  movement  in 
the  moisture  toward   any  empty  space  would  take  place ; 
and  the  moisture  of  the  rock  around,  on  reaching  the  space 


FORMATION   OP   VEINS.  317 

or  fissure,  would  lose  its  mineral  material  by  its  crystalliza- 
tion against  the  walls ;  the  place  of  that  which  was  thus 
lost  would  be  resupplied  at  once  by  other  portions,  with  the 
same  result;  and  thus  a  constant  current  would  be  kept  up 
as  long  as  the  supply  held  out,  or  until  the  cavity  or  fissure 
were  filled.  In  the  filling  of  veins,  the  material  comes  mostly 
from  the  rock  adjoining  some  part  of  the  fissure. 

However  minute  the  quantity  of  any  material  in  the 
adjoining  rock,  even  if  it  be  wholly  undistinguishable  by 
any  chemical  investigation,  the  penetrating  heated  and 
mineralized  moisture  would  find  it,  and,  taking  it  into  solu- 
tion, convey  it  to  the  forming  vein.  Gold,  and  the  material 
of  emeralds  and  other  metals  and  gems,  have  thus  been 
gathered  into  veins. 

The  kind  of  crystallizations  in  the  fissure  would  depend 
largely  on  the  heat  present  and  the  nature  of  the  rock 
adjoining;  and  the  heat  would  depend  on  the  depth  of  the 
fissure.  If  the  vein  reached  down  to  depths  of  intense 
heat,  where  cooling  would  be  exceedingly  slow,  the  materials 
would  be  more  coarsely  crystallized  than  if  only  to  shallow 
depths. 

Metallic  ores  may  often  rise  in  the  fissures,  in  vapors  or 
solutions,  from  depths  far  below  those  at  which  they  are 
deposited. 

Some  strata,  owing  to  their  nature,  might  afford  almost 
nothing  for  the  fissure,  and  the  filling  of  this  part  would 
then  come  from  the  portions  above  or  below. 

3.  Simple  and  banded  veins. — Veins  filled  by  this  lateral 
inflow  of  material  would  sometimes  be  uniform  in  texture 
throughout,  as  in  many  quartz  veins  or  seams;  or  they 
might  be  banded,  like  most  metallic  veins  (p.  30).  In  the 
formation  of  the  latter,  the  infiltrating  process  might  bring 
in  for  a  while  one  kind  of  mineral,  as  feldspar,  and  deposit 
it  over  the  walls  of  the  fissure ;  then,  through  a  modification 
of  the  temperature,  or  some  other  change,  quartz;  then,  an 


318  DYNAMICAL   GEOLOGY. 

ore  of  lead,  or  one  of  zinc,  or  one  of  copper;  then  quartz 
again,  or  calcite;  and  so  on  until  the  vein  was  filled. 

In  these  ways  argillaceous  and  talcose  schists  have  been 
filled  with  quartz  veins  or  seams,  the  repositories  of  gold 
and  of  various  ores.  (These  auriferous  quartz  veins  in 
schists  arc  often  only  the  filling  of  cavities  opened  between 
the  layers,  and  which  are  due  to  the  contortions  the  schists 
underwent  during  the  uplifting,  folding,  and  metamorphic 
process.)  By  similar  methods  granitic  and  various  metallic 
veins  have  been  formed  in  rocks  of  other  kinds. 

Thus  the  earth's  metals  have  been  gathered  from  rocks, 
in  which  they  were  disseminated  in  such  infinitesimal  quan- 
tities as  to  be  of  no  service  to  art,  into  generous  veins,  and 
so  placed  within  reach  of  the  miner. 

V.  MOVEMENTS  IN  THE  EARTH'S  CEUST,  AND 
THEIR  CONSEQUENCES. 

The  subjects  here  included  are  the  following : — 

1.  Origin  of  changes  of  position  and  level  in  the  earth's 
crust  or  rocks. 

2.  Origin  of  cleavage  and  jointed  structure  in  rocks. 

3.  Earthquakes. 

4.  Origin  of  the  earth's  general  features,  and  of  the  suc- 
cessive phases  in  its  history. 

1.  CHANGES  IN  POSITION  AND  LEVEL. 

Change  of  level  may  proceed  from  undermining,  either  by 
subterranean  waters  (p.  281),  or  by  volcanic  ejections  (p. 
309).  But  the  results  of  these  causes  are  comparatively 
local. 

The  causes  of  more  comprehensive  character,  usually  ap- 
pealed to  in  order  to  explain  the  origin  of  the  earth's  moun- 
tains and  its  oscillations  of  level,  are  the  following : — 

1.  Vapors  suddenly  evolved  beneath  some  portion  of  the  earth's 
crust. — This  cause  has  been  commonly  regarded  as  of  the 


CHANGES   OF   LEVEL.  319 

highest  importance,  especially  with  reference  to  the  eleva- 
tion of  mountains.  There  are  two  difficulties  with  regard 
to  it.  (1.)  No  open  cavities  of  sufficient  extent  for  the  pur- 
pose can  be  proved  to  exist  beneath  mountains  where  such 
vapors  could  spread  and  act.  (2.)  If  the  explosion  were  to 
take  place, — as,  for  example,  beneath  the  Andes, — the 
mountains  would  not  stay  up  on  a  mere  bed  of  condensiblo 
vapors ;  they  are  very  heavy,  and  require  solid  support. 

2.  Weight  of  the  accumulations  of  sedimentary  formations  in 
progress  over  any  region,  as  the  Appalachian. — This  cause 
might   possibly  produce   subsidence   in   a  region  like   the 
Appalachians,  and  some  uplifts  either  side  as  a  secondary 
effect  from  the  lateral  pushing  which  such  a  subsidence 
might  occasion.    But,  although  the  subsidence  in  the  Appa- 
lachian region  greatly  exceeded  the  elevations  (p.  155)  there 
were  some  elevations  alternating  with  the  subsidences  in 
the  course  of  the  Paleozoic  ages;  and,  later,  in  the  progress 
of  the  formation  of  the  mountains,  a  series  of  flexures  on  a 
great  scale,  over  the  whole  breadth  of  the  region,  was  pro- 
duced in  addition  to  elevations  (p.  156);  and  such  effects 
cannot  proceed  from  mere  weight  or  gravitation. 

3.  Expansion  and  contraction  from  change  of  temperature. — 
If  a  portion  of  the  crust,  or  of  its  rocks,  becomes  heated 
from  the  action  of  heat  below,  elevation  will  result,  because 
an  increase  of  heat  causes  expansion ;  and  expansion  must 
show  itself  in  a  rising  of  the  surface.      Conversely,  if  a 
heated  region  cools,  there  will  be  contraction ;  and  this  con- 
traction may  cause  two  effects  :  (1)  a  sinking  in  the  surface; 
(2)  a  fracturing  of  the  rocks,  or  shrinkage-cracks.     If  there 
are  no  fractures  produced,  the  whole  result  will  appear  in 
the  sinking. 

This  cause  of  change  of  level  acts  with  extreme  slowness. 

The  subsidence  and  elevation  of  the  region  of  the  Temple 
of  Serapis,  on  the  coast  of  Italy  just  north  of  Naples,  have 
been  attributed  to  this  cause. 


320  DYNAMICAL   GEOLOGY. 

4.  Tension  in  the  earth's  crust  resulting  from  the  contraction 
of  the  globe. — In  the  remarks  on  the  Appalachian  revolution 
(p.  160),  it  was  shown  that  the  effects  proved  beyond  ques- 
tion— (1)  the  action  of  lateral  pressure;  (2)  that  this  lateral 
pressure  was  exerted  in  the  earth's  crust,  and  in  a  direction 
from  the  Atlantic  Ocean,  or  at  right  angles  to  the  course  of 
the  mountains ;  (3)  that  it  was  exceedingly  slow  or  gradual 
in  action.  This  slow-acting  pressure,  as  in  the  third  cause 
above  explained,  is  a  power  residing,  through  some  cause, 
in  the  crust  itself  of  the  earth. 

The  facts  observed  in  the  Appalachians  are  common  facts 
all  over  the  globe  wherever  there  are  uplifted  rocks  or 
mountains.  Nearly  all  tilted  rocks  are  actually  folded 
rocks.  The  flexures  vary  in  extent  from  the  slightest  arch- 
ing of  the  strata  to  bold  and  lofty  close-pressed  folds,  as 
illustrated  on  pages  41,  42.  This  flexed  condition  could 
have  been  produced  only  by  lateral  action  or  pressure,  as  a 
result  of  the  cause  alluded  to.  This  cause  has,  therefore, 
produced  universal  effects  over  the  globe. 

The  facts  in  Geology  leave  little  room  for  doubt  that  the 
earth  was  once  in  fusion,  and  has  been  through  all  time  a 
cooling  globe.  If  it  has  been  a  cooling  globe,  it  has  been 
undergoing  contraction,  or  a  gradual  diminution  of  size, 
just  as  a  globe  of  glass  or  lead  will  become  smaller  on  slow 
cooling.  Now,  in  the  case  of  a  cooling  sphere,  if  an  exterior 
hard  crust  be  early  formed, the  contraction  afterwards  going 
on  within  will  bring  a  great  strain  on  this  crust,  because  it 
is  unyielding  and  cannot  accommodate  itself  to  the  contrac- 
tion in  progress;  and  this  strain,  if  the  crust  be  not  thick 
enough  to  stand  firm,  will  result  either  in  breaking  the 
crust  and  pulling  inward  some  portions  and  so  pressing 
other  parts  out,  or  in  making  the  crust  to  rise  into  folds. 
In  a  drying,  and  therefore  contracting,  apple,  the  skin 
becomes  folded,  because  flexible.  In  a  drop  of  glass  (called 
a  Prince  Rupert's  drop)  which  has  been  formed  by  rapid 


CHANGES   OF   LEVEL.  321 

cooling  (the  outside  thereby  being  first  cooled),  the  whole 
is  under  powerful  tension  or  strain.  The  exterior  is  so  hard, 
of  so  uniform  texture,  and  of  so  even  surface,  that  it  cannot 
become  folded,  and  yet  it  remains  unbroken;  but  if  the 
faintest  scratch  of  a  file  be  made,  so  as  to  disturb  the  equi- 
librium in  the  mass,  the  whole  goes  to  fragments,  even  with 
explosion.  The  scratch  of  the  file  takes  out  particles  from 
the  surface,  and  acts  like  the  taking  out  of  a  line  of  stones 
from  a  heavily  weighted  arch ;  the  destruction  is  in  principle 
the  same  as  in  the  case  of  the  arch. 

In  a  cooling  sphere  like  the  earth  there  must  have  always 
been  a  tension  or  strain  in  the  crust  from  this  cause ;  and, 
as  the  earth  is  not  a  glass  globe  of  even  texture  and  surface, 
the  cause  should  have  produced  fractures  and  flexures, 
bulgings  and  sinkings,  over  its  various  parts,  and  at  various 
times  in  the  course  of  the  earth's  history;  while  gentle  oscil- 
lations of  level  in  the  crust  must  have  been  in  constant 
progress. 

5.  Sufficiency  of  the  last-mentioned  cause. — This  cause  is  a 
sufficient  cause  for  all  flexures  of  strata,  because  it  is  indefi- 
nite in  power  and  very  slowr  in  its  action.  A  sudden  force 
would  throw  strata  into  a  chaos.  But  experiment  has  proved 
that  by  an  exceedingly  gradual  movement  any  bed  of  rock, 
however  inflexible,  especially  if  moistened  and  heated,  and 
even  cold  ice,  may  be  made  to  rise  into  an  arch,  and  then 
into  a  series  of  arches  or  folds,  by  a  slowly  acting  lateral 
pressure. 

This  cause  is  one  that  affords  a  firm  support  for  the  lifted 
continent  or  mountain-chain  as  it  rises;  for  in  its  action 
one  portion  of  the  earth's  crust  is  pushed  up  by  another,  and 
the  former,  therefore,  rests  on  the  mass  by  means  of  which 
it  was  raised.  It  remains  where  it  is  placed  by  the  irresist- 
ible pressing  force. 

This  cause  is  sufficient  to  have  made  the  mountains 
of  the  globe.  Mountains  are  relatively  very  small  eleva- 


322  DYNAMICAL   GEOLOGY. 

tions  on  the  earth's  surface.  Etna,  although  10,000  feet 
high,  would  stand  up  but  one-tenth  of  an  inch  on  a  globe 
110  feet  in  circumference,  or  35  feet  in  diameter, — as 
large  as  many  a  capacious  house;  and  one-hundredth  of  an 
inch  would  correspond  on  such  a  globe  to  1000  feet,  which 
is  the  mean  height  of  all  the  continents.  The  wrinkles  on 
an  orange  are  proportionally  larger  than  those  of  the  earth 
or  her  mountains :  the  earth  has  relatively  the  smoother 
surface. 

It  is  obvious,  therefore,  that  the  height  or  extent  of 
mountain-elevations  is  no  difficulty  before  such  a  force  as 
that  contemplated.  Chains  as  lofty  as  the  Himalayas, 
valleys  as  deep  as  the  profoundest  oceanic  basin,  flexures  as 
numerous  and  close  as  those  of  the  Appalachians,  Juras,  and 
other  chains,  and  fractures  and  faults  thousands  of  feet  in 
depth,  may  all  proceed  from  this  one  universal  and  ever- 
acting  cause.  The  changes  of  level  now  in  progress  in 
Sweden,  Greenland,  and  some  other  northern  regions,  may 
be  due  to  its  present  power. 

6.  Change  of  water-level  may  be  caused  by  change  of  level  in 
the  bottom  of  the  oceanic  basins. — Changes  of  level  are  ordi- 
narily measured  by  reference  to  the  water-level, — that  is,  the 
level  of  the  ocean.  Thus,  if  a  region  is  100  feet  above  the 
ocean  in  one  period  and  200  in  a  following,  the  first  inference 
Is  that  the  land  has  been  elevated  100  feet.  It  is  plain, 
however,  that  this  inference  is  correct  only  in  case  the 
bottom  of  the  ocean  has  remained  unchanged  in  level.  The 
oceanic  area  is  three  times  as  large  as  that  of  the  continents; 
and  if  the  earth's  crust  beneath  the  oceans  were  to  sub- 
side until  the  average  subsidence  was  200  feet,  the  water- 
level  would  sink  away  from  the  land  to  a  level  200  feet 
below  the  present  level.  There  is  no  reason  why  the  oceanic 
part  of  the  crust  should  not  have  been  as  liable  to  change 
of  level  by  subsidence  as  that  of  the  land  by  elevation ;  in 
fact,  there  is  strong  evidence  for  believing,  as  mentioned 


SLATY  CLEAVAGE   AND   JOINTS.  323 

beyond,  that  the  oceanic  basin  has  always  been  the  more 
sinking  portion  of  the  crust,  or  that  most  subject  to  subsi- 
dence. It  is,  therefore,  essential  for  accurate  conclusions,  in 
cases  of  apparent  elevation,  that  the  possibility  of  changes 
over  the  oceans  should  be  considered.  It  is  probable  that 
the  present  average  height  of  the  continental  lands  above 
the  ocean,  or  1000  feet,  is  wholly  owing  to  the  sinking  of 
the  ocean's  bed  which  was  in  progress  through  the  successive 
geological  ages. 

2.  SLATY  CLEAVAGE  AND  JOINTS. 

1.  Slaty  cleavage. — On  page  36  it  has  been  stated  that  the 
lamination,  or  slaty  cleavage,  of  the  great  beds  of  roofing- 
slate  does  not,  as  in  shales,  conform  in  direction  to  the 
original  layers  or  beds,  but,  on  the  contrary,  is  oblique  to  the 
bedding  and  sometimes  nearly  at  right  angles  to  it.  As 
slates  were  originally  shales,  some  change  has  come  over 
them  in  the  process  of  metamorphism,  which  has  almost 
or  quite  obliterated  the  original  lamination  and  produced 
another  in  a  new  and  transverse  direction. 

The  shales  during  a  metamorphic  process  are  not  only 
hardened  and  rendered,  it  may  be,  semi-crystalline,  but  they 
are  also  uplifted  or  folded.  This  uplifting  and  folding  is  a 
result  of  long-continued  lateral  pressure,  as  explained  on 
the  preceding  pages.  The  slaty  cleavage  results  directly  from 
the  lateral  pressure  attending  the  uplifting  and  flexing,  and 
is  at  right  angles  to  the  direction  of  the  pressure.  Tyndall  has 
found  that  even  beeswax  may  be  rendered  lamellar  in 
structure  by  pressure  alone;  and  if  this  is  possible  with  a 
substance  of  so  uniform  texture  as  beeswax,  there  is  no 
question  about  it  with  regard  to  clayey  rocks.  The  pressure 
tends  to  force  all  lamellar  particles,  as  scales  of  mica,  or 
flattened  grains  of  sand,  into  parallel  planes  having  the 
direction  just  stated,  and  also  to  flatten  out  all  air-spaces  in 
the  same  direction ;  and  in  these  ways  the  pressure  is  enabled 

28* 


324  DYNAMICAL   GEOLOGY. 

to  produce  the  slaty  structure.  The  same  structure  actually 
exists  in  the  ice  of  many  glaciers,  and  from  essentially  the 
same  cause. 

2.  Joints. — Joints  in  rocks  are  described  on  page  35  as 
planes  of  fracture  descending  to  great  depths,  and  as  being 
systematically  parallel  in  the  same  region,  and  also  in  great 
numbers.  This  parallelism  is  similar  to  the  parallelism  in 
the  slaty  structure,  and  both  have  the  same  origin, — the 
lateral  pressure  attending  movements  in  the  earth's  crust. 
Joints  occur  in  rocks  of  any  kind,  even  coarse  conglomerates 
and  granites  as  well  as  sandstones,  limestones,  slates,  and 
shales,  and  also  in  rocks  that  are  not  inclined  or  but  little 
so.  AVhile  the  slaty  structure  is  an  effect  of  successive 
movements  in  the  action  of  pressure,  the  joints  may  proceed 
both  from  such  movements  and  from  a  simple  yielding  to  a 
progressing  tension  or  strain.  This  force,  acting  from  a 
common  direction  through  a  long  period,  produces  in  the 
end  a  series  of  deep  fractures,  parallel  in  course  and  there- 
fore one  in  system.  Other  joints  at  right  angles  to  this 
system  may  result  simultaneously,  making  a  transverse 
system.  Or  the  action  of  the  same  force  in  a  later  period 
or  age,  from  a  different  direction,  may  cause  a  system  of  joints 
oblique  to  the  first.  Thus,  two  or  more  systems  of  joints 
may  be  produced  in  the  rocks  of  the  same  region. 

Joints  and  slaty  cleavage  are,  therefore,  effects  of  the 
great  and  universal  power  which  has  caused  the  oscillations, 
uplifts,  and  flexures  in  the  earth's  crust. 

3.  EARTHQUAKES. 

1.  Nature  of  earthquake-vibrations. — Earthquakes  are  vibra- 
tions in  the  material  of  the  earth's  crust.  A  shock  or 
concussion  produced  by  a  fracture  or  movement  at  any 
point  causes  vibrations  in  the  rocks,  and  these  vibrations 
travel  outward  from  this  point  until  they  finally  die  out. 


EARTHQUAKES.  325 

The  vibrations  in  ice  made  by  skaters  may  be  heard  for 
miles  if  the  ear  be  placed  close  to  the  ice,  because  these 
vibrations  travel  far  in  a  layer  of  such  material.  So  it  is, 
also,  in  the  earth's  rocks,  although  they  are  of  less  even 
texture  and  surface. 

The  vibrations  are  of  different  kinds:— (1)  a  simple 
shaking,  without  any  actual  displacement  in  the  rocks; 
(2)  a  more  powerful  vibration,  where  there  are  both  a  shaking 
and  a  displacement,  as  when  a  shove,  fault,  or  uplift  sud- 
denly takes  place ;  (3)  very  rapid  vibrations,  causing  the 
sensation  of  sound. 

2.  Effects  of  earthquakes  over  the  land. — Earthquakes  are 
well  known  to  result  often  in  the  destruction  of  buildings, 
or  even  cities ;   in  the  opening  of  profound  cracks  in  the 
ground,  in  which  great  numbers  of  people  are  sometimes 
engulfed;  in  the  displacement  of  rocks  and  trees,  and  start- 
ing of  avalanches  of  gravel  and  stones  down  precipices. 

3.  Earthquake    oceanic   waves. — An    earthquake-vibration, 
when  communicated  to  the  ocean,  causes  great  and  powerful 
waves,  which  sometimes  travel  for  thousands  of  miles.    The 
earthquake  at  Valdivia  on  the  coast  of  Chili,  in  1837,  pro- 
duced a  series  of  waves  which  deluged  the  eastern  shores 
of  Hawaii,  6000  miles  distant;  and  an  earthquake  in  1854, 
at  Simoda  in  Japan,  sent  waves  across  the  Pacific  to  Oregon 
and  California,  which  were  detected  there  by  the  self-regis- 
tering tide-gauges  of  the  Coast  Survey. 

Oceanic  earthquake-waves,  in  1746,  swept  up  the  coast  of 
Peru,  and  carried  a  frigate  from  the  harbor  of  Callao  several 
miles  over  the  land,  besides  sinking  23  vessels ;  and  during 
an  earthquake  on  the  coast  of  Spain,  in  1755,  the  sea  rushed 
up  the  land  in  a  wave  40  feet  high  in  the  Tagus  and  60  feet 
at  Cadiz ;  and  the  same  wave  was  8  to  10  feet  high  on  the 
coast  of  Cornwall,  England. 

These  earthquake-waves  have  been  an  agency  of  great 
power  and  of  very  important  results  in  the  course  of  the 


326  DYNAMICAL   GEOLOGY. 

earth's  ancient  history,  deluging  the  land,  destroying  life, 
both  of  the  sea  and  land,  and  sweeping  away  beaches  and 
stratified  deposits. 

4.  Causes  of  Earthquakes. — Whatever  causes  are  capable  of 
producing  changes  of  level  or  position  in  the  earth's  crust 
may  be  causes  of  earthquakes.  Thus,  the  undermining  of 
strata,  the  evolution  of  vapors  about  volcanoes,  tidal  or 
other  movements  in  the  earth's  liquid  interior,  tension 
from  change  of  temperature,  as  in  local  cases,  or  in  tho 
earth's  slow  cooling,  must  have  each  produced  their  earth- 
quakes. The  last  cause  must  have  been  the  most  common 
and  comprehensive,  if  it  is  the  cause  of  the  larger  part  of 
the  oscillations  and  uplifts  over  the  earth.  It  may  be  the 
cause  of  the  more  powerful  and  extensive  earthquakes  of 
the  present  day,  since  tension  within  from  the  progress  of 
cooling  cannot  yet  have  ceased.  The  cracking  sounds  in  a 
stove-pipe  as  a  furnace  is  rapidly  heating  or  cooling  are 
a  result  of  that  tension  from  expansion  or  contraction  which 
accompanies  change  of  temperature;  for  there  is  a  strain 
produced,  and  then  a  yielding  with  loud  sound.  They 
exemplify,  on  a  small  scale,  the  lighter  kind  of  earthquakes 
resulting  from  the  earth's  secular  refrigeration. 

According  to  Prof.  Pcrrcy  of  Dijon,  there  is  some  corre- 
spondence between  the  occurrence  of  earthquakes  and  the 
times  of  the  ocean's  tidal  movements,  and  he  infers,  conse- 
quently, that  there  are  tides  in  the  earth's  interior  liquid 
corresponding  to  those  of  the  ocean,  making  themselves 
manifest  in  earthquake-vibrations.  Further  investigation 
appears  to  be  required  to  establish  this  as  an  actual  causo 
of  earthquakes  at  the  present  time. 

4.    ORIGIN    OF    THE    EARTH'S    GENERAL    FEATURES,    AND    OF 
THE  SUCCESSIVE  PHASES  IN  ITS  HISTORY. 

]    General  laws  as  to  the  Earth's  features. 
The  first  two  of  the  following  laws  have  been  stated  and 


EVOLUTION   OF   THE   EARTH'S   FEATURES.  327 

explained  on  pages  8  to  11.  The  others  are  illustrated  in 
the  course  of  the  volume.  It  should  be  understood  that  the 
border  region  of  a  continent  includes  the  ridges  of  the  border 
mountains  and  the  country  which  lies  between  them  and 
the  adjoining  seacoast.  Thus,  the  western  border  region 
of  North  America  is  that  lying  between  the  summits  of  the 
Rocky  Mountains  and  the  Pacific  coast,  an  area  300  to  800 
miles  wide  j  and  the  eastern  is  that  extending  from  the 
western  ridges  of  the  Appalachians  to  the  Atlantic,  an  area 
200  to  300  miles  in  width. 

(1.)  The  continents  have  in  general  high  borders  and  a 
low  interior,  and  are,  therefore,  basin-shaped. 

(2.)  The  highest  border  faces  the  largest  ocean. 

(3.)  The  effects  of  heat  after  Azoic  time  are  more  marked 
along  the  border  regions  of  the  continents  than  over  their 
interior.  It  is  sufficient,  in  illustration  of  this  law,  to 
refer  to  the  fact  that  nearly  all  the  metamorphism  of  North 
American  rocks,  after  that  of  Azoic  time,  took  place  either 
in  the  Atlantic  or  the  Pacific  border  regions ;  and  that  the 
volcanoes  of  this  and  the  other  continents,  with  a  rare 
exception,  are  confined,  and  have  alwaj^s  been  confined,  to 
the  border  regions  of  those  continents,  and  are  absent  from 
the  interior  regions.  One  exception  exists  in  central  Asia, 
in  the  Thian-Chan  Mountains.  The  volcanoes  of  Europe 
and  western  Asia  pertain  to  the  region  bordering  on  the 
Mediterranean  and  Eed  Sea. 

(4.)  The  effects  of  heat  are  most  marked  on  the  border 
region  adjoining  the  largest  ocean.  This  law  is  also  exem- 
plified on  all  the  continents.  The  great  ocean — the  Pacific 
— has  a  girt  of  volcanoes,  as  stated  on  page  300 ;  the  small 
Atlantic,  almost  none.  In  North  America  a  large  number 
of  volcanoes,  from  10,000  to  18,000  feet  in  height,  exist  in  the 
western  border  region,  but  not  one  east  of  the  summit  of 
the  Rocky  Mountains;  metamorphic  rocks,  and  those 
igneous  rocks  that  have  been  ejected  through  fissures,  are 


328  DYNAMICAL    GEOLOGY. 

almost  the  sole  effects  of  igneous  action  found  in  the  At- 
lantic border  region. 

In  South  America  there  are  similar  facts :  the  volcanoes 
of  the  Pacific  border  region  are  very  numerous,  and  vary 
from  25,000  feet  in  height  to  10,000  and  under.  On  the 
Atlantic  side  there  are  none.  In  Africa  there  is  a  small 
volcanic  region  on  the  coast  adjoining  the  Gulf  of  Guinea, 
in  the  Cameroons  Mountains;  but  a  number  of  large  volca- 
noes exist  in  eastern  Africa  through  Abyssinia  and  the  Red 
Sea. 

In  the  great  Orient  there  arc  hundreds  of  volcanoes  on 
the  Pacific  side,  in  the  outer  range  of  heights  constituting 
the  islands  off  the  coast,  as  the  Philippines,  Japan,  the 
Kuriles,  etc.,  and  in  Kamtchatka;  but  none  on  the  coast  of 
Norway,  and  only  a  few  small  regions  in  Europe,  and  these, 
as  has  been  said,  are  connected  \vuii  the  Mediterranean 
region. 

(5.)  The  transverse  mediterranean  seas  of  the  world  abound 
in  volcanoes. — The  East  Indies  between  Australia  and  Asia, 
the  Eed  and  Mediterranean  seas  between  Africa  and  Europe, 
the  AVcst  Indies,  as  well  as  Central  America,  between  North 
and  South  America,  are  notedly  volcanic  areas.  The  volca- 
noes of  the  Mediterranean  region  occur  in  Spain,  France, 
Germany,  Italy,  Greece,  Syria,  and  Armenia. 

2.   Orijin  of  the  Earth's  Features,  and  Phases  of  Progress. 

1.  The  cause  universal  in  action. — The  conformity  of  the 
continents  in  their  reliefs  to  one  model  (p.  9)  proves  some 
common  method  of  formation;  and,  as  the  continents  occupy 
one-third  of  the  earth's  surface,  this  method  of  formation 
must  have  been  dependent  on  some  world-wide  cause. 

Since,  moreover,  the  forms  of  the  continents  have  a 
direct  relation  to  the  extent  of  the  ocean  (a  relation  so  close 
that  there  is  almost  an  exact  proportion  between  the  eleva- 
tion of  the  border  region  of  the  continents  and  the  capacity 


.      EVOLUTION    OF   THE   EARTH'S   FEATURES.  329 

)f  the  adjoining  ocean),  both  must  have  resulted  from  the 
?ame  universal  method  of  development. 

2.  Continents  and  oceans  outlined  in  the  beginning. — The 
making  of  the  continents  according  to  a  model   implies  a 
regular  or  systematic  course  of  progress  throughout  the 
earth's  history.     If  the  ocean  and  continents  had  at  times 
changed  places  (if  Asia,  for  example,  had  ever  been  the  area 
of  the  deep  ocean,  and  the  bed  of  the  Pacific  the  dry  land 
of  a  continent,  and  thus  oceans  and  continents  had  alter- 
nated with  one  another),  the  comprehensive  relation  between 
the  extent  of  the  oceans  and  the  heights  of  the  continental 
borders  would  have  been  impossible.     Direct  observation 
has  proved,  moreover,  that  the  continent  of  J^orth  America 
was  in  actual  existence,  and  of  nearly  or  quite  its  present 
extent,  by  the  close  of  the  Azoic  age,  if  not  before    (p.  84); 
that,  although  mostly  submerged,  it  lay  in  the  Primordial 
period  near  the  surface,  part  constituting  the  Azoic  dry 
land,  part  rising  as  sand-banks,  beaches,  and  dunes  above 
the  tides,  a  large  part  in  shallow  waters  within  reach  of 
the  waves,  while  other  portions  were  at  somewhat  greater 
depths. 

The  above  proposition  is  proved  also  by  the  whole  course 
of  geological  progress,  the  great  fact  in  which  is  that  the 
elevating  and  oscillating  forces  which  were  in  action  in 
Azoic  times  continued  to  be,  for  the  most  part,  the  same  in 
direction  through  all  subsequent  time  to  the  close  of  the 
Tertiary.  (See  pages  77,  146,  245). 

The  law  of  form,  the  law  of  progress,  and  the  law  of  rela- 
tion to  the  oceans,  each  and  all  afford  decisive  proof,  there- 
fore, that  the  continents  were  fixed  in  their  positions  in 
the  beginning,  and  determined  at  the  same  time,  also,  in 
their  main  outline;  and,  if  the  outlines  of  the  continents 
were  fixed,  those  of  the  oceans  were  so  also,  since  they  aro 
one  and  the  same. 

3.  Oneness  of  the  cause. — One  cause   acting  continuously 


330  DYNAMICAL   GEOLOGY. 

from  the  beginning  of  the  earth's  crust  to  the  <  i  of  geolo- 
gical history  has,  therefore,  originated  by  concurrent  move- 
ments the  oceanic  basin  and  the  continental  plateaus.  This 
cause  has  not  merely  raised  the  continental  areas  and  sunk 
the  oceanic.  It  has  made  their  mountains  and  their  plains. 
It  has  evolved,  not  isolated  or  scattered  heights,  but  heights 
in  ranges  and  chains,  and  placed  them  with  so  much  system 
over  the  surface  that  a  continent  has  as  truly  its  type  of 
form  as  an  animal.  In  each  case  there  is  the  same  evidence 
of  a  system  of  evolution  or  development,  starting  from  a 
condition  of  mcmbcrless  simplicity,  and  ending  in  a  complex 
structure  in  which  every  part  has  harmonious  reference  to 
a  specific  purpose. 

4.  Nature  and  mode  of  action  of  the  cause. — In  explaining 
the  origin  of  mountains,  the  complete  efficiency  and  uni- 
versality of  one  great  cause  was  pointed  out.  This  cause — 
contraction  from  cooling — appears  to  have  all  the  require- 
ments, as  far  as  they  can  reside  in  any  physical  cause,  that 
are  necessary  for  the  grander  result  here  in  view, — the 
development  of  the  earth's  physical  features.  It  has  acted 
uninterruptedly  through  all  time.  It  must  have  acted 
with  simultaneous  and  accordant  results  throughout  the 
whole  crust,  oceanic  and  continental.  But,  while  every- 
where in  simultaneous  and  systematic  movement,  there 
have  been  produced  a  diversity  of  effects,  and  a  diversity 
under  system. 

In  a  cooling  globe,  the  part  which  earliest  became  cold 
and  rigid  would  not  afterwards  yield,  under  the  influence 
of  the  progressing  contraction,  as  readily  as  the  rest,  and 
would  therefore  remain  comparatively  firm  while  the  other 
part  was  gradually  subsiding.  There  might  hence  be  from 
the  first  a  firmer  or  more  stable  portion,  and  a  sinking  or 
depressed  portion;  and  thus  would  begin  the  continental 
and  the  oceanic  areas.  The  waters  of  such  a  globe  would  be 


EVOLUTION    OP   THE   EARTH'S   FEATURES.  331 

deepest  in  the  depressed  portion,  if  not  wholly  contained 
within  it. 

If,  then,  the  oceanic  portions  of  the  crust  were  the  great 
contracting  areas,  and  the  continental  plateaus  the  parts 
comparatively  stable,  or  those  contracting  least,  the  sinking 
of  the  crust  of  the  former  would  bring  the  greatest  strain 
against  the  borders  of  the  rigid  portion,  that  is,  the  borders 
of  the  continental  plateaus.  Here,  therefore,  the  lateral  press- 
ure or  pushing  action  would  show  its  greatest  effects: 
(1)  in  upliftings  of  the  crust;  (2)  in  foldings  and  fractures; 

(3)  in    metamorphism    through    escaping    internal   heat; 

(4)  in  igneous  ejections  through  fissures  and  volcanic  vents. 
The  continents  subjected  to  such  a  force  would  have  their 
border  regions  elevated  thereby,  and  would  thus  receive 
that  basin-like  shape  which  characterizes  them.     Moreover, 
as  the  deepest  and  largest  oceanic  basin  is  a  result  of  the 
gi-eatest  amount  of  contraction  over  the  largest  area,  the 
mountains  on  the   border  of  the  largest  ocean  would   be 
highest,  the  fractures  deepest,  and  the  volcanoes,  since  they 
are  opened  over  deep  fractures,  most  numerous,  as  have 
been  shown  to  be  true  (pp.  (10,  300). 

The  cause  considered  may  also  produce  mountains  over 
the  interior  of  a  continent,  as  it  does  minor  uplifts,  and 
especially  so  if  the  continent  be  of  great  breadth.  For  con- 
traction must  have  been  ever  in  progress  beneath  the  con- 
tinental plateaus,  as  well  as  the  oceanic  basin.  It  is  hence 
natural  that  the  great  Orient,  GOOO  miles  in  width  from 
Britain  to  Japan,  should  have  its  Urals  as  a  nearly  north 
and  south  chain  between  Europe  and  Asia. 

The  facts  and  the  theory  seem  thus  to  be  in  unison. 
There  can  be  no  doubt  that  plications,  fractures,  and  moun- 
tain-lifting have  resulted  through  tension  or  lateral  pressure 
in  the  crust  from  some  cause.  No  cause  of  such  tension 
has  been  pointed  out  but  that  of  gradual  contraction 
through  the  cooling  of  the  earth.  The  cause  would  give 


332  DYNAMICAL   GEOLOGY. 

systematic  results;  it  would  produce  general  uniformity  of 
action  and  progress  through  successive  ages ;  and  it  would 
lead  to  that  family  likeness  which  subsists  between  the 
continents,  while  admitting  also  of  those  diversities  which 
distinguish  them. 

5.  Catastrophes  and  revolutions,  or  abrupt  transitions  in  his- 
tory.— A  cause  producing  the  oscillations  of  the  earth's  crust 
and  the  elevation  of  mountains  would  also  occasion  catas- 
trophes to  the  life  of  the  globe,  and  abrupt  transitions  in 
the  series  of  strata. 

If  the  raising  of  a  continent  from  the  ocean,  or  of  a  large 
portion  of  it,  were  to  take  place  under  the  action  of  such  a 
cause,  an  extinction  of  marine  life  would  bo  a  necessary 
consequence;  or,  if  a  sinking  of  a  continent  beneath  the 
waves  should  occur,  an  extinction  of  terrestrial  life  would 
result.  Changing  simply  the  depth  of  the  water  might  also 
cause  extinctions,  since  the  oceanic  species  living  between 
high  and  low  tide  level  (or  in  the  littoral  zone,  as  it  is  called) 
are  mostly  different  from  those  below;  and  those  living 
between  low-water  and  90  feet  (or  in  the  Laminarian  zone) 
are  almost  all  different  from  those  of  greater  depths. 

These  oscillations  might  cause  the  extinction  of  life,  also, 
by  changing  the  climate  of  the  globe,  as  explained  on  page 
256. 

Moreover,  all  changes  of  level,  causing  submergence  or 
emergence  of  the  land,  or  even  varying  the  depth  of  water, 
would  change  more  or  less  the  courses  of  currents  in  the  seas 
and  the  region  of  wave-action,  and  would  consequently 
change  the  hinds  of  rocks  in  progress,  as  from  sand-beds  to 
shales,  or  to  conglomerate,  and  the  reverse.  Again,  an 
extermination  of  the  animal  life  (corals,  crinoids,  &c.)  of  a 
continental  sea  by  any  oscillation  or  other  cause  would  stop 
the  formation  of  limestones ;  and  the  extermination  (as  by 
submergence)  of  the  plants  of  the  land  would  cut  short  the 
coal-plant  accumulation,  to  be  resumed  again  only  when 


EVOLUTION    OF   THE    EARTH'S    FEATURES.  333 

the  land  should  bo  anew  in  a  condition  to  grow  the  terres- 
trial vegetation  of  marshes. 

Under  such  a  cause,  there  would  be,  at  long  intervals, 
epochs  of  grander  catastrophes,  resulting  in  mctamorphism, 
in  great  fractures  and  foldings,  and  in  the  raising  of  moun- 
tains. The  tension  arising  from  contraction  in  such  a  crust 
would  go  on  accumulating  for  long  pei'iods  before  it  would 
be  sufficient  to  overcome  the  resistance  and  cause  great 
disturbances ;  and  when  a  yielding  finally  took  place,  then 
the  grander  scries  of  catastrophes  would  happen.  There 
was  one  grand  epoch  of  general  metamorphism  and  folding 
at  or  near  the  close  of  the  Azoic.  Through  the  Paleozoic 
t'icrc  were  various  oscillations  of  level,  and,  at  a  few  times, 
disturbances  and  uplifts,  with  probably  some  metamorphism 
(as  in  the  Green  Mountains  after  the  Lower  Silurian) ;  but 
no  general  epoch  of  change  occurred  in  eastern  North 
America  or  over  the  world  until  the  close  of  the  Paleozoic, 
when  the  Appalachian  revolution  took  place. 

After  this  epoch  of  the  Appalachian  revolution,  there 
were,  through  Mcsozoic  time,  changes  of  level  or  uplifts  of 
limited  extent;  but  not  until  the  Cretaceous  period  was 
drawing  to  its  close  did  another  grand  epoch  begin, — the 
one  in  which  the  life  of  the  Cretaceous  world  ended,  and 
the  great  mountains  of  the  continents  were  mostly  made 
(p.  202). 

3.  Illustrations  from  North  America. 

1.  Simplicity  of  action  in  North  America. — The  continent 
of  North  America  stands  isolated  from  all  others,  having  an 
ocean  on  the  east,  an  ocean  on  the  west,  the  small  Arctic 
sea  on  the  north,  and  the  Pacific  with  partly  the  Atlantic — 
not  South  America — on  the  south.  It  is,  therefore,  in  the 
best  possible  condition  for  exemplifying  the  law  of  origin  of 
the  continental  features.  For  if  the  extent  of  the  oceans  is 
an  approximate  measure  of  the  elevating  forces  engaged, 


334  DYNAMICAL   GEOLOGY. 

this  open  exposure  to  the  ocean  on  all  its  sides  should  give 
the  forces  their  best  opportunity  for  undisturbed  or  regular 
results. 

Europe,  on  the  contrary,  lies  between  oceans  and  conti- 
nents, and  is,  therefore,  complex  in  its  rocks  and  mountains. 

2.  Method  of  action,  and  its  progress. — The  two  systems  of 
forces  engaged  in  the  progress  of  North  America  were  those 
of  the  Atlantic  and  Pacific,  the  latter  the  greatest.  Under 
their  action  the  V-shaped  Azoic  dry  land  (map.  page  73) 
was  first  defined,  one  branch  stretching  northeastward  to 
Labrador  and  the  other  northwestward  to  the  Arctic,  and 
thus  facing  respectively  the  Atlantic  and  Pacific.  It  fol- 
lows, from  the  courses  of  the  arms  of  the  V,  that  the 
Atlantic  force  acted  mainly  from  the  southeastward  and 
the  Pacific  from  the  southwestward,  and  the  two,  therefore, 
nearly  at  right  angles  to  one  another.  It  is  also  apparent 
that  the  Pacific  force  even  then  was  the  greater,  and  hence 
the  Pacific  Ocean  the  larger;  for  the  northwestward  branch 
of  the  V  is  far  the  longer. 

Thus  the  Azoic  nucleus  was  outlined,  and  the  portion  of 
Hudson's  Bay  determined  within  the  arms  of  the  V.  From 
this  nucleal  dry  land,  pi'Ogress  went  forward  southeastward 
or  toward  the  Atlantic,  and  southwestward  or  toward  the 
Pacific,  successive  formations  being  added  under  gentle 
oscillations,  and  the  dry  land  gradually  extending  under 
changes  of  level  caused  mainly  by  the  same  forces.  Then, 
when  Paleozoic  time  was  closing,  appeared  the  Appalachian 
chain  and  its  many  ridges  parallel  to  the  eastern  branch  of 
the  Azoic  heights,  and  along  the  Kocky  chain  parallel  to  the 
western  branch ;  thus  doubling  the  V,  and  proving  that  the 
forces  were  still  the  same  in  direction  as  in  Azoic  time. 
The  Appalachian  chain  follows  in  its  direction  quite  closely 
the  Azoic  coast-line ;  for  the  Green  Mountain  portion  ex- 
tends north  and  south,  like  the  border  of  the  Azoic  penin- 
sula in  northern  New  York,  and  then  the  New  Jersey  and 


EVOLUTION    OF    THE    EARTH'S    FEATURES.  -335 

Pennsylvania  portions  bend  around  nearly  to  the  east  and 
west,  or  parallel  with  the  southern  border  of  the  New  York 
Azoic.  South  of  this  the  chain  takes  again  its  normal 
direction,  or  from  northeast  to  southwest.  Later  still,  roso 
the  trap  ridges  of  the  Mesozoic  on  the  Atlantic  border 
(p.  1G5),  making  another  parallel  to  the  eastern  branch,  or 
tripling  the  V  on  the  east,  and  even  repeating  all  tho 
Appalachian  bends  just  mentioned. 

Again,  on  the  Pacific  side,  other  ranges  were  made  parallel 
to  the  course  of  the  Rocky  Mountain  chain ;  among  them, 
the  Sierra  Nevada  and  Cascade  range,  the  latter,  with  its 
many  volcanoes,  adding  new  parallels  to  the  western  branch 
of  the  Azoic.  The  mass  of  the  Eocky  Mountains  also  roso 
to  its  full  height  above  the  ocean. 

Each  added  range,  as  is  seen,  proves  that  the  mountain- 
making  forces  continued  to  act  from  the  same  directions  as 
in  Azoic  time. 

The  intersection  of  effects  of  the  Atlantic  and  Pacific 
forces  may  be  distinguished  over  the  interior  of  North 
America;  for  the  courses  of  the  uplifts  of  the  Coal  formation 
in  Illinois  and  the  trend  of  Florida  are  parallel  to  the  Pacific 
border,  and  the  line  between  these  two  intersects  the  Appa- 
lachian chain  in  eastern  Tennessee.  Again,  there  is  an 
uplift  of  the  Lower  Silurian  about  Cincinnati,  which  appears 
to  have  been  produced  by  the  combined  action  of  the  two 
forces;  and  it  is  of  interest  to  note  that  the  Pacific  and 
Atlantic  forces  here  meet  at  a  point  which  is  four  times 
more  distant  from  tho  coast  of  the  Pacific  or  larger  ocean 
than  it  is  from  that  of  the  Atlantic  or  smaller  ocean. 

Thus  the  continent  made  progress,  adding  layer  after 
layer  to  the  rocks  over  its  surface,  and  range  after  range 
in  parallel  lines  to  its  heights,  until  finally  the  continental 
area  reached  its  limit,  and  the  great  interior  basin  had 
its  mountain-borders  completed : — on  the  east,  the  low  Appa- 
lachians, and  the  trap  ridges  of  the  Mesozoie ;  on  the  west, 


836  DYNAMICAL    GEOLOGY. 

the  massive  and  lofty  Kocky  chain,  with  its  parallel  crests 
and  ridges,  and  nearer  the  ocean  a  chain  containing,  north 
of  California  (in  the  part  called  the  Cascade  range),  a  num- 
ber of  lofty  volcanic  peaks,  and  to  the  south  (Sierra  Ne- 
vada) consisting  mostly  of  metamorphic  rocks. 

It  has  been  explained  on  page  234  that,  when  thus  com- 
pleted, there  occurred  an  apparent  change  in  the  region 
moved  by  the  forces.  The  high-latitude  oscillations  of  tho 
Post-tertiary  began  (p.  219).  But  the  Pacific  and  Atlantic 
forces  may  have  occasioned  these  new  movements.  For  if, 
in  the  course  of  the  changes  though  the  geological  ages,  tho 
portions  of  the  continental  crust  in  lower  latitudes,  thick- 
ened by  the  successive  formations,  and  stiffened  by  moun- 
tain-chains and  metamorphism,  had  become  less  yielding 
than  those  of  higher  latitudes,  the  pressure  from  contraction 
would  have  produced  its  oscillations  in  the  latter  rather 
than  the  former. 

Thus,  the  evolution  of  the  features  of  the  surface,  even  to 
the  terraces  made  along  the  river-valleys,  as  the  era  of  Man 
opened,  may  have  taken  place  through  one  system  of  forces 
originating  in  one  single  cause, — the  earth's  contraction  from 
cooling. 

CONCLUDING  EEMAEKS. 

Geology  may  seem  to  be  audacious  in  its  attempts  to  un- 
veil the  mysteries  of  creation.  Yet  what  it  reveals  aro 
only  some  of  the  methods  by  which  the  Creator  has  per- 
formed his  will ;  and  many  deeper  mysteries  it  leaves  un- 
touched. 

It  brings  to  view  a  perfect  and  harmonious  system  of  life, 
but  affords  no  explanation  of  the  origin  of  life,  or  of  its 
species,  or  of  any  of  nature's  forces. 

It  accounts  for  the  forms  of  continents ;  but  it  tells  nothing 
as  to  the  source  of  that  arrangement  of  the  wide  and  nar«- 


CONCLUSION.  337 

row  continents  and  wide  and  narrow  oceans  that  was  neces- 
sary to  the  grand  result  (p.  11). 

It  teaches  that  strata  were  made  in  many  successions  as 
the  continents  lay  balancing  near  the  water's  level,  some- 
times just  above  the  surface,  sometimes  a  little  below;  but 
it  does  not  explain  how  it  happened  that  the  amount  of 
water  was  of  exactly  the  right  quantity  to  fill  the  great 
basin,  and  admit  of  oscillations  of  the  land  beneath  or  above 
its  surface  by  only  small  changes  of  level  ;  for  if  the  water 
had  been  a  few  hundred  feet  below  the  level  it  now  has, 
the  continents  would  have  remained  mostly  without  their 
marine  strata,  and  the  plan  of  progress  would  have  proved 
a  failure ;  or  if  as  much  above  its  present  level,  the  land 
through  the  earlier  ages  would  have  been  sunk  to  depths 
comparatively  lifeless,  with  no  less  fatal  results  both  to 
the  series  of  rocks  and  the  system  of  marine  and  terrestrial 
life;  and  in  the  end  there  would  have  been  broad  and 
narrow  strips  of  dry  land  and  archipelagos,  in  place  of  the 
expanded  Orient  and  Occident. 

It  may  be  said  to  have  searched  out  the  mode  of  develop- 
ment of  a  world.  Yet  it  can  point  to  no  physical  cause  of 
that  prophecy  of  Man  which  runs  through  the  whole  his- 
tory; which  was  uttered  by  the  winds  and  waves  at  their 
work  over  the  sands,  by  the  rocks  in  each  movement  of  the 
earth's  crust,  and  by  every  living  thing  in  the  long  succes- 
sion, until  Man  appeared  to  make  the  mysterious  announce- 
ments intelligible.  For  the  body  of  Man  was  not  made 
more  completely  for  the  service  of  the  soul,  than  the  earth, 
in  all  its  arrangements  from  beginning  to  end,  for  the  spi- 
ritual being  that  was  to  occupy  it.  In  Man,  the  bones  are 
not  merely  the  jointed  framework  of  an  animal,  but  a  frame- 
work shaped  throughout  with  reference  to  that  erect  struc- 
ture which  befits  and  can  best  serve  Man's  spiritual  nature. 
The  feet  are  not  the  clasping  and  climbing  feet  of  a  mon- 
key ;  they  are  so  made  as  to  give  firmness  to  the  tread  and 


338  CONCLUSION. 

dignity  to  the  bearing  of  the  being  made  in  God's  image. 
The  hands  have  that  fashioning  of  the  palm,  fingers,  and 
thumb,  and  that  delicacy  of  the  sense  of  touch,  which  adapt 
them  not  only  to  feed  the  mouth,  but  to  contribute  to  the 
wants  of  the  soul  and  obey  its  promptings.  The  arms  are 
not  for  strength  alone, — for  they  are  weaker  than  in  many  a 
brute, — but  to  give  the  greater  power  and  expression  to  the 
thoughts  that  issue  from  within.  The  face,  with  its  express- 
ive features,  is  formed  so  as  to  respond  not  solely  to  the 
emotions  of  pleasure  and  pain,  but  to  shades  of  sentiment 
and  interacting  sympathies  the  most  varied,  high  as  heaven 
and  low  as  earth, — aye,  lower,  in  debased  human  nature. 
And  the  whole  being,  body,  limbs,  and  head,  with  eyes  look- 
ing not  towards  the  earth,  but  beyond  an  infinite  horizon, 
is  a  majestic  expression  of  the  divine  feature  in  Man,  and  of 
the  infinitude  of  his  aspirations. 

So  with  the  earth,  Man's  world-body.  Its  rocks  were  so 
arranged,  in  their  formation,  that  they  should  best  serve 
Man's  purposes.  The  strata  were  subjected  to  metamor- 
phism,  and  so  crystallized,  that  he  might  bo  provided  with 
the  most  perfect  material  for  his  art, — his  statues,  temples, 
and  dwellings;  at  the  same  time,  they  were  filled  with  veins, 
in  order  to  supply  him  with  gold  and  silver  and  other  trea- 
sures. The  rocks  were  also  made  to  enclose  abundant  beds 
of  coal  and  iron  ore,  that  Man  might  have  fuel  for  his 
hearths  and  iron  for  his  utensils  and  machinery.  Moun- 
tains were  raised  to  temper  hot  climates,  to  diversify  the 
earth's  productiveness,  and,  pre-eminently,  to  gather  the 
clouds  into  river-channels,  thence  to  moisten  the  fields  for 
agriculture,  aiford  facilities  for  travel,  and  supply  the  world 
with  springs  and  fountains. 

The  continents  were  clustered  mostly  in  one  hemisphere 
to  bring  the  nations  into  closer  union;  and  the  two  having 
climates  and  resources  the  best  for  human  progress — the 
northern  Orient  and  Occident — were  separated  by  a  narrow 


CONCLUSION..  339 

ocean,  that  the  great  mountains  might  be  on  the  remoter 
borders  of  each,  and  all  the  declivities,  plains,  and  rivers  bo 
turned  towards  one  common  channel  of  intercourse.  So 
also,  the  species  of  life,  both  of  plants  and  animals,  were 
appointed  to  administer  to  Man's  necessities,  moral  as  well 
as  physical. 

Besides  these  beneficent  provisions,  the  forces  and  laws 
of  nature  were  particularly  adapted  to  Man,  and  Man  to 
those  laws,  so  that  he  should  be  able  to  take  the  oceans, 
rivers,  and  winds  into  his  service,  and  even  the  more  subtle 
agencies,  heat,  light,  and  electricity;  and  the  adjustments 
were  made  with  such  precision  that  the  face  of  the  earth  is 
actually  fitted  hardly  less  than  his  own  to  respond  to  his 
inner  being : — the  mountains  to  his  sense  of  the  sublime, 
the  landscape,  with  its  slopes,  its  trees,  its  flowers,  to  his 
love  of  the  beautiful,  and  the  thousands  of  living  species, 
in  their  diversity,  to  his  various  emotions  and  sentiments. 
The  whole  world,  indeed,  seems  to  have  been  made  almost 
a  material  manifestation,  in  multitudinous  forms,  of  the  ele- 
ments of  his  own  spiritual  nature,  that  it  might  thereby  give 
wings  to  the  soul  in  its  heavenward  aspirings.  It  may 
therefore  be  said  with  truth  that  Man's  spirit  was  con- 
sidered in  the  ordering  of  the  earth's  structure  as  well  as  in 
that  of  his  own  body. 

It  is  hence  obvious  that  the  earth's  history,  which  it  is 
the  object  of  Geology  to  teach,  is  the  true  introduction  to 
human  history. 

It  is  also  certain  that  science,  whatever  it  may  accom- 
plish in  the  discovery  of -causes  or  methods  of  progress,  can 
take  no  steps  towards  setting  aside  a  Creator.  Far  from 
such  a  result,  it  clearly  proves  that  there  has  been  not  only 
an  omnipotent  hand  to  create,  and  to  sustain  physical  forces 
in  action,  but  an  all-wise  and  beneficent  Spirit  to  shape  i.11 
events  towards  a  spiritual  end. 

Man  may  well  feel  exalted  to  find  that  he  was  the  final 


340  CONCLUSION. 

purpose  when  the  word  went  forth  in  the  beginning,  LET 
LIGHT  BE.  And  he  may  thence  derive  direct  personal  assu- 
rance that  all  this  magnificent  preparation  is  yet  to  have  a 
higher  fulfilment  in  a  future  of  spiritual  life.  This  assu- 
rance from  nature  nay  S99m  fceb.e.  .•_  ot  it  is  at  least  suffi- 
cient to  strengthen  faith  m  that  Book  of  books  in  which  the 
promise  of  that  life  and  "  the  way"  are  plainly  set  forth. 


APPENDIX. 


A.— Catalogue  of  American  Localities  of  Fossils. 

The  following  catalogue  of  American  localities  of  fossils  contains 
only  some  of  the  more  important,  and  is  intended  for  the  conve- 
nience especially  of  the  student-collector. 

LOCALITIES  OF  FOSSILS. 

Potsdam  sandstone. — Swan  ton,  Vt. ;  Braintree,  Mass. ;  Keeseville 
(at  "High  Bridge"),  Alexandria,  N.Y. ;  Chiques  Eidge,  Pa.;  Falls 
of  St.  Croix,  Osceola  Mills,  Trempaleau,  Wisconsin  ;  Lansing,  Iowa ; 
St.  Ann's,  Isle  Perrot,  C.W. ;  near  Beauharnois  on  Lake  St.  Louis, 
C.E. 

Calciferous. — Point  Levis,  Mingan  Islands,  Philipsburg,  and  near 
Beauharnois,  C.E. ;  Grand  Trunk  Railway  between  Brockville  and 
Prescott,  St.  Ann's,  Isle  Perrot,  C.W. ;  Amsterdam,  Port  Plain, 
Canajoharie,  Chazy,  Lafargeville,  Ogdensburgh,  N.Y. 

Chazy  limestone. — Chazy,  Galway,  Westport,  N.Y. ;  Island  of  Mon- 
treal, C.E.,  (1  to  3  miles  north  of  "  the  Mountain.") 

Bird's-eye  limestone. — Amsterdam,  Little  Falls,  Fort  Plain,  Adams, 
Watertown,  N.Y. 

Black  River  limestone. — Watertown,  N.Y. ;  Ottawa,  C.W. ;  Island 
of  Montreal,  and  near  Quebec,  C.E. 

Trenton  limestone. — Adams,  Watertown,  Boonville,  Turin,  Jackson- 
burgh,  Little  Falls,  Lowville,  Middleville,  Fort  Plain,  Trenton 
Falls,  N.Y.;  Pine  Grove,  Aaronsburg,  Potter's  Fort,  Milligan's 
Cove,  Pa. ;  Highgate  Springs,  Vt. ;  Montmorency  Falls  and  Beau- 
port  Quarries  near  Quebec,  Island  of  Montreal  (quarries  N.  of  the 
city),  C.E. ;  Ottawa,  Belleville,  Trenton  (G.  T.  R.  R.,  W.  of  Kings- 
ton), C.W.;  Copper  Bay,  Mich.;  Elkader  Mills,  Turkey  River, 
Dubuque,  Iowa ;  Falls  of  St.  Anthony,  St.  Paul,  Mineral  Point, 
Cassville,  Beloit,  Quimby's  Mills  near  Benton,  Wis. ;  Warren, 
Illinois.  341 


342  APPENDIX. 

Utica  slate.— Turin,  Martin  sburgh,  Lorraine,  Worth,  TTtica,  Cold 
Spring,  Oxtungo  and  O.^quago  Creeks  near  Fort  Plain,  Mohawk, 
House's  Point,  N.Y. ;  Eideau  Kiver  along  E.  E.  at  Ottawa,  bed  of 
river  two  miles  above,  C.W. 

Hudson  River  group. — Pulaski,  Eome,  Lorraine,  and  Boonville, 
N.Y. ;  Penn's  Valley,  Milligan's  Cove,  Pa. ;  Oxford,  Cincinnati,  0. ; 
Madison,  Ind. ;  Anticosti,  opposite  Three  Eivers,  C.E. ;  Weston  on 
the  Humber  Eiver,  nine  miles  W.  of  Toronto,  C.W. ;  Little  Mako- 
queta  Eiver,  Iowa ;  Savannah,  Green  Bay,  Wis. ;  Scales  Mound, 
111. ;  Drummond's  Island,  Mich. 

Medina  sandstone. — Lockport,  Lewiston,  Medina,  Eochester,  N.Y. ; 
Long  Narrows  below  Lewistown,  Pa. 

Clinton  group.— Lewiston,  Lockport,  Eeynolds'  Basin,  Brockport, 
Eochester,  Wolcott,  New  Hartford,  N.Y. ;  Thorold  on  Welland 
Canal,  Hamilton,  Ancaster,  C.W. 

Niagara. — Lewiston,  Lockport,  Eochester,  Wolcott,  N.Y. ;  Tho- 
rold, Hamilton,  Ancaster,  C.W. ;  Anticosti,  C.E. ;  Arisaig,  Nova 
Scotia ;  Eacine,  Waukesha,  Wis. ;  Marblehead  on  Drummond's 
Island,  Michigan.  (Coralline  limestone. — Schoharie,  N.Y.) 

Onondaga  Salt  Group. — Buffalo,  Williamsville,  Waterville,  Jeru- 
salem Hill  (Herkimer  co.),  N.Y. 

Leclaire  limestone. — Leclaire,  111. 

"  Golf  or  "Guelph"  formation. — Gait,  Guelph  (G.  T.  E.  E.),  C.W. 

Lower  Helderberg  limestones. — Dry  Hill,  Jerusalem  Hill  (Herkimer 
co.),  Sharon,  East  Cobleskill,  Judd's  Falls,  Cherry  Valley,  Carlisle, 
Schoharie,  Clarksville,  Athens,  N.Y. ;  Gaspe,  C.E. 

Oriskany  sandstone. — Oriskany,  Vienna,  Carlisle,  Schoharie,  Cats- 
kill  Mountains,  N.Y. ;  Cumberland,  Md. ;  Moorestown  and  Franks- 
town,  Pa. 

Cauda-Galli  Grit.— Schoharie  (Fucoides  Cauda-Galli),  N.Y. 

Schoharie  Grit. — Schoharie,  Cherry  Valley,  N.Y. 

Upper  Helderberg  limestones.— Black  Eock,  Buffalo,  Williamsville, 
Lancaster,  Clarence  Hollow,  Stafford,  Le  Eoy,  Caledonia,  Mendon, 
Auburn,  Onondaga,  Cassville,  Babcock's  Hill,  Schoharie,  Cherry 
.  Valley,  Clarksville,  N.Y. ;  Port  Colborne,  and  near  Cayuga,  C.W. ; 
Columbus,  Delaware,  Sandusky,  0. ;  Mackinac,  Little  Traverse  Bay, 
Dundee,  Monguagon,  Mich. 

Marcellus  shales. — Lake  Erie  shore,  ten  miles  S.  of  Buffalo,  Lancas- 
ter, Alden,  Avon,  Leroy,  Marcellus,  Manlius,  Cherry  Valley,  N.Y. 


APPENDIX.  343 

Hamilton  group.— Lake  Erie  shore,  Eighteen  Mile  Creek,  Ham- 
burgh, Alden,  Darien,  York,  Moscow,  Bloomfield,  Bristol,  Seneca 
Lake,  Cayuga  Lake,  and  Skaneateles  Lake,  Pompey,  Cazenovia, 
Delphi,  Bridgewater,  Richland,  Cherry  Valley,  Seward,  West  ford, 
Milford,  Portlandville,  N.Y. ;  VVidder  Station  (G.  T.  R.  R.),  near 
Port  Sarnia,  C.W. ;  New  Buffalo,  Independence,  Iowa ;  Rock 
Island,  111. ;  Thunder  Bay,  Little  Traverse  Bay,  Mich. ;  Nictaux, 
Bear  River,  Moose  River,  Nova  Scotia. 

Genesee  slate. — Banks  of  Seneca  and  Cayuga  Lakes,  Lodi  Falls, 
Mount  Morris,  two  miles  S.  of  Big  Stream  Point,  Yates  co.,  N.Y. 

Portage  group. — Eighteen  Mile  Creek,  Lake  Erie  shore,  Chautau- 
qua  Lake,  Genesee  River  at  Portage.  Flint  Creek,  Cashaqua  Creek, 
Nunda,  Seneca  and  Cayuga  Lakes,  N.Y. 

Chemung  group. — Rockville,  Philipsburgh,  Jasper,  Greene,  Che- 
mung  Narrows,  Troopsville,  Elmira,  Ithaca,  Waverly,  Hector,  En- 
field,  N.Y.;  Gaspe,  C.E. 

Catskill group. — Fossils  rare. — Richmond's  quarry  above  Mt.  Upton 
on  the  Unadilla,  Oneonta,  Oxford,  Steuben  co.  south  of  the  Canis- 
teo,  N.Y. 

Subcarloniferous. — Burlington,  Keokuk,  Iowa;  Quincy,  Warsaw, 
Alton,  Kaskaskia,  Chester,  111. ;  Bloomington,  Spergen  Hill,  Ind. ; 
Hannibal,  St.  Genevieve,  St.  Louis,  Mo.;  Willow  Creek,  Battle 
Creek,  Holland,  Grand  Rapids,  Mich. ;  Mauch  Chunk,  Pa. ;  Red 
Sulphur  Springs,  Pittsburg  Landing,  Tenn. ;  Big  Bear  and  Little 
Bear  Creeks,  Big  Crippled  Deer  Creek,  Miss. ;  Clarksville,  Hunts- 
ville,  Ala. ;  Windsor,  Horton,  Nova  Scotia. 

Carboniferous. — South  Joggins,  Pictou,  Sydney,  Nova  Scotia ; 
Wilkesbarre,  Shamokin,  Tamaqua,  Potisville,  Minersville,  Tremont, 
Greensburg,  Carbondale,  Port  Carbon,  Lehigh,  Trevorton,  Johns- 
town, Pittsburg,  Pa.  ;  Pomeroy,  Marietta,  Zanesville,  Cuyahoga 
Falls,  Athens,  Ohio ;  Charlestown,  Clarksburg,  Kanawha  Salines, 
Wheeling,  Va. ;  Saline  Company's  mines,  Gallatin  co.,  Terre  Haute, 
Morris,  Springfield,  111. :  Bell's,  Casey's,  and  Union  Mines,  Critten- 
den  co. ;  Hawesville  and  Lewisport,  Hancock  co. ;  Breckinridge, 
Giger's  Hill,  Mulford's  Mines,  and  Thompson's  Mine,  Union  co. ; 
Providence  and  Madisonville,  Hopkins  co.;  Bonharbour,  Daviess 
co.,  Ky. :  Muscatine,  Alpine  Dam,  Iowa ;  Leavenworth,  Indian 
Creek,  Grasshopper  Creek,  Juniata,  Manhattan,  Kansas. 


344  APPENDIX. 

Triassic. — Southbury,  Middlefield,  Portland,  Conn.;  Turner's 
Falls,  Sunderland,  Mass. ;  Phoenixville,  Pa. ;  Richmond,  Va. ; 
Deep  River  and  Dan  River  coal-fields,  N.C. 

Cretaceous. — Upper  Freehold,  Middletown,  Marlboro',  Blue  Ball, 
Deal,  Squankum,  Shark  River,  Monmouth  co. ;  Pemberton,  Vin- 
centon,  Burlington  co. ;  Blackwoodtown,  Camden  co. ;  Mullica  Hill, 
Gloucester  co. ;  Woodstown,  Mannington,  Salem  co. ;  New  Egypt, 
Ocean  co.,  N.  J. :  Warren's  Mill,  Itawamba  co. ;  Tishomingo  Creek, 
R.  R.  cuts,  Hare's  Mill,  Carrollsville,  Tishomingo  co. ;  Plymouth 
Bluff,  Lowndes  co. ;  Chawalla  Station  (M.  &  C.  R.  R.),  Ripley,  Tip- 
pah  co. ;  Noxubee,  Macon,  Noxubee  co. ;  Kemper,  Pontotoc  and 
Chickasaw  counties,  Miss. :  Fox  Hills,  Sage  Creek,  Long  Lake,  Great 
Bend,  Cheyenne  River,  etc.,  Nebraska. 

Eocene. — Everywhere  in  Tippah  co. :  Yockeney  River,  New 
Prospect  P.  O.,  Winston  co. ;  Marion,  Lauderdale  co. ;  Enterprise, 
Clarke  co. ;  Jackson ;  Satartia,  Yazoo  co. ;  Homewood,  Scott  co. : 
Chickasawhay  River,  Clarke  co. ;  Winchester,  Red  Bluff  Station, 
Wayne  co. ;  Vicksburg,  Amsterdam,  Brownsville,  Warren  co. ; 
Brandon,  Byram  Station,  Rankin  co. ;  Paulding,  Jasper  co.,  Miss. : 
Claiborne,  Monroe  co. ;  St.  Stephen's,  Washington  co.,  Ala. :  Charles- 
ton, S.C. ;  Tampa  Bay,  Florida ;  Fort  Washington,  Fort  Marlbo- 
rough,  Piscataway,  Md. ;  Marlbourne,  Va. ;  Brandon,  Vt. ;  Cafiada 
de  las  Uvas,  Cal. 

Miocene. — Gay  Head,  Martha's  Vineyard,  Mass. ;  Shiloh,  Jericho, 
Cumberland  co.,  N.J. ;  St.  Mary's,  Easton,  Md. ;  Yorktown,  Suffolk, 
Smithfield,  Richmond,  Petersburg,  Va. ;  Astoria,  Willamette  River, 
Oregon ;  San  Pablo  Bay,  Ocoya  Creek,  San  Diego,  Monterey,  San 
Joaquin  and  Tulare  Valleys,  Cal. ;  White  River,  Upper  Missouri 
Region. 

Pliocene.— Ashley  and  Santee  Rivers,  S.C. ;  Platte  and  Niobrara 
Rivers,  Upper  Missouri. 

B.— Geological  Implements,  Specimens,  etc. 

1.  Implements. — The  student  requires  for  his  geological  excur- 
sions and  research  the  following  implements : — 

(1.)  A  hammer  of  the  form  in  fig.  373.  The  face  should  be  flat, 
and  nearly  square,  with  its  edges  sharp  instead  of  rounded.  The 
socket  for  the  handle  should  be  large,  that  the  handle  may  be 


APPENDIX.  345 


strong.  The  hammer,  for  ordinary  excursions,  should  weigh  1£ 
pounds  exclusive  of  the  handle ;  the  handle  should  be  about  12 
inches  long.  Another  is  required  for  trimming  specimens,  weigh- 
ing half  a  pound. 

Fig.  373.  Fig.  374. 


(2.)  A  hammer  in  the  form  of  a  small  pick,  like  fig.  374,  for  pick- 
ing open  the  layers  of  slaty  rocks,  etc.  It  should  be  7  or  8  inches 
long,  and  terminate  above  in  a  chisel-like  edge  transverse  to  the 
handle.  The  length  of  handle  may  be  13  or  14  inches. 

(3.)  A  steel  chisel,  6  inches  long,  1  inch  wide  at  top,  and  tapering 
to  a  narrow  edge,  or  wedge-shaped.  Also,  another  half  of  these 
dimensions. 

(4.)  A  clinometer,  with  magnetic  needle  attached.  See  page  40.  The 
best  kind  is  a  pocket  instrument  in  the  form  of  a  watch,  about  2J 
inches  in  diameter. 

(5.)  A  small  magnet.  A  magnetized  blade  of  a  pocket-knife  is  a 
good  substitute. 

(G.)  A  measuring-tape  50  feet  long.  The  field  geologist  should 
know  accurately  the  measurements  of  his  own  body,  his  height, 
length  of  limbs,  step  or  pace,  that  he  may  use  himself,  whenever 
needed,  as  a  measuring-rod. 

(7.)  In  many  cases,  a  pick,  a  croiff-bar,  a  sledge-hammer  of  4  to  8 
pounds'  weight,  and  the  means  of  blasting,  are  necessary. 

(8.)  A  strong  sack-coat,  with  vefy  large  and  stoutly  made  side- 
pockets. 

(9.)  Besides  the  above,  a  barometer  and  surveyor's  instruments  are 
occasionally  required.  Of  the  latter,  a  hand-level  is  a  very  desirable 
instrument  for  determining  small  elevations  by  levelling.  It  is  a 
simple  brass  tube,  with  cross-hairs,  bubble  and  mirror. 


346  APPENDIX. 

2.  Specimens. — Specimens  for  illustrating  the   kinds  of  rocks 
should  be  carefully  trimmed  by  chipping  to  a  uniform  size,  pre- 
viously determined  upon :  3  inches  by  4  across,  and  1  inch  through, 
is  the  size  commonly  adopted.     In  the  best  collections  of  rocks,  the 
angles  are  squared  and  the  edges  made  straight  with  great  preci- 
sion.    They  should  have  a  fresh  surface  of  fracture,  with  no  bruises 
by  the  hammer.     It  is  often  well  to  leave  one  side  in  its  natural 
weathered  state,  to  show  the  effects  of  weathering. 

Specimens  of  fossils  will,  of  course,  vary  in  size  with  the  nature  of 
the  fossil.  When  possible,  the  fossil  should  be  separated  from  the 
rock ;  but  this  must  be  done  with  precaution,  lest  it  be  broken  in 
the  process,  and  should  not  be  attempted  unless  the  chances  are 
strongly  in  favor  of  securing  the  specimen  entire.  The  skilful  use 
of  a  small  chisel  and  hammer  will  often  expose  to  view  nearly  all 
of  a  fossil  when  it  is  not  best  wholly  to  detach  it.  When  the  fossils 
in  a  limestone  are  silicified  (a  fact  easily  proved  by  their  scratching 
glass  readily  and  their  undergoing  no  change  in  heated  acid),  they 
may  be  cleaned  by  putting  them  into  an  acid,  and  also  applying 
heat  very  gently,  if  effervescence  does  not  take  place  without  it. 
The  best  acid  is  chlorohydric  (muriatic)  diluted  one-half  with 
water. 

Collections  both  of  rocks  and  fossils  should  always  be  made  from 
rocks  in  place,  and  not  from  stray  boulders  of  uncertain  locality. 

3.  Packing. — For  packing,  eacu  specimen  should  be  enveloped 
separately  in  two  or  three  thicknesses  of  strong  wrapping-paper. 
This  is  best  done  by  cutting  the  paper  of  such  a  size  that  when 
folded  around  the  specimen  the  ends  will  project  two  inches  (more 
or  less,  according  to  the  size  of  the  specimen) ;  after  folding  the 
paper  around  it,  turn  in  the  projecting  ends  (as  the  end  of  the 
finger  of  a  glove  may  be  turned  in),  and  the  envelop  will  need  no 
other  securing.     Pack  in  a  strong  box,  pressing  each  specimen, 
after  thus  enveloping  it,  firmly  into  its  place,  crowding  wads  of 
paper  between  them  wherever  possible,  and  make  the  box  abso- 
lutely full  to  the  very  top  (by  packing-material  if  the  specimens  do 
not  suffice),  so  that  no  amount  of  rou«ih  usage  by  wagon  or  cars  on 
a  journey  of  a  thousand  miles  would  cause  the  least  movement 
inside. 


APPENDIX.  347 

4.  Labelling. — A  label  should  be  put  inside  of  each  envelop,  sepa- 
rated from  the  specimen  by  a  thickness  or  more  of  the  paper.    The 
label  should  give  the  precise  locality  of  the  specimen,  and  the  par- 
ticular stratum  from  which  taken,  if  there  is  a  series  of  strata  at  the 
place ;  it  should  also  have  a  number  on  it  corresponding  to  a  num- 
ber in  a  note-book,  where  fuller  notes  of  each  are  kept,  together 
with  the  details  of  stratification,  dip,  and  strike,  sections,  plans, 
changes  or  variations  in  the  rocks,  and  all  geological  observations 
that  may  be  made  in  the  region.     A  specimen  of  rock  or  fossil  of 
unknown  or  uncertain  locality  is  of  very  little  value. 

5.  Note-Book. — The  note-book  should  have  a  stiff  leather  cover, 
and   be  made   of   rather   thick   smooth   writing-paper,   good    for 
sketching  as  well  as  for  writing.     Five  inches  by  three  and  a  half 
is  a  convenient  size.     A  kind  made  of  prepared  paper,  and  pro- 
vided with  a  zinc-pointed  pencil,  is  often  sold  for  the  purpose,  and 
is  excellent  until  it  gets  perchance  a  fall  into  the  water,  when  the 
notes  that  may  have  been  carefully  made  will  be  pretty  surely 
obliterated.     If  the  geologist  is  a  draftsman,  he  may  also  need  a 
portfolio  for  carrying  larger  paper;  but  the  small  note-book  will,  in 
general,  answer  every  purpose. 


INDEX. 


NOTE.— The  asterisk  after  the 
illustrated  by  a  figure. 


iber  of  a  page  indicates  that  the  subject  referred  to  to 


Acalephs,  58.* 
Acanthoteutbis,  177.* 

Apennines,  origin  of,  203,  218 
Appalachian  Coal  area,  117. 

Bathygrnathus  borealis,  170.* 
Beach-tonnations,  226,  287,  289. 

Acephals,  56.* 

revolution,  155. 

nuts,  fossil,  210* 

Acrodus  minimus,  52.* 

Appalachians,    formation    of 

structure,  31.* 

nobilis,  52.* 
Acrogens,  60. 

155,  246,  247. 
folded  rocks  of,  41,*  156.* 

Beaver,   former    geographical 
range  of,  241. 

Carboniferous,  126. 

thickness    of    formations 

Belemniteila  mucronata,  193.* 

Devonian,  108. 

of,  80,  86,  92,  102. 

Belemnites,  177,*  193.* 

Actinia,  57.* 

Araucariae,  62. 

Bernese  Alps,  292. 

Actinocrinus      proboscidialis, 

Archseoniscus  Brodiei,  178.* 

Bilin,  infusorial  bed  of,  -210. 

131.* 

Archimedes  reversa,  131.* 

Birds,  50. 

JEpiornis,  extinction  of,  241. 

Arctic  climate  in  Jurassic,  187. 

first  of.  170. 

Ages  in  Geology,  63. 

climate  in  Carboniferous,          of  Connecticut  valley,  172.* 

Age,  Carboniferous,  116. 

149. 

of  Solenholen,  183,  201. 

Devonian,  lOt. 

climate  in  Cenozoic,  234. 

Tertiary,  213. 

Mammalian,  205. 

coal  area,  119. 

Bituminous  coal.  18,  123. 

of  Coal  Plants,  116. 

Argillaceous  schist.  24. 

Bivalves,  56.* 

of  Fishes,  lOi. 

Argillite,  24. 

Black-river  limestone,  86. 

of  Man,  236.                        1  Artesian  wells,  281,  300. 

Black  slate,  of  Devonian,  106. 

of  Mollu  sks,  78.                 !  Articulates,  49,  53  * 

Blattina  venusta,  132.* 

Reptilian,  162. 

first  of  terrestrial,  107. 

Bois  Glacier.  292. 

Silurian,  78. 
Albite,  15. 

Asaphus  gigas,  89.* 
Ascidians,  57 

Bore,  285. 
Boulders,  220,  279. 

Algae,  60. 

Astarte  Conradi,  211.* 

transported   by   glaciers, 

Alluvial  dero-its,  224,  273. 

Athyris  subtilita,  131.* 

294. 

Alps,  elevation  of,  203,  218. 

Atmosphere,agency  of,  in  caus- 

Brachiopods, 56  * 

America,    N.,    Geography   of. 

ing  geological  changes, 

Carboniferous,  131.* 

See  GEOORAPHT. 

271. 

Devonian,  111.* 

Ammonites,  175.* 

Atolls,  268.* 

Primordial,  81.* 

Humphrsysianus,  175.* 

Atrypa  aspera,  112.* 

Silurian,  88,*  97.* 

Jason,  175* 

Aulopora  cornuta,  111.* 

Brakes,  60. 

Placenta,  193* 

Australia,  basaltic  columns  of, 

Brandon  fossil  fruits,  20&.* 

of  Mesozoic,  200. 

311.* 

Breccia,  22. 

tornatus,  176.* 

Australian  character  of  vege- 

Bryozoans, 57.* 

Amphibians,  50. 

tation  in  Tertiary  Eu- 

Carboniferous, 130.* 

Ampbipods,  54.* 

rope,  219. 

Devonian,  111.* 

Amphitherium,  183.* 

Marsupials    of,   in    Post- 

Silurian,  81,*  88,*  98* 

Amygdaloid,  311. 
Anatifa,  54* 
Andalusite,  17.* 

tertiary,  233. 
Avicula  emacerata,  97.* 
Trentonensis,  88.* 

Buffalo,   former  geographical 
range  of,  241. 
Buhrstone,  Tertiary,  208. 

Andes,  origin  of,  203,  219. 

Azoic  Time,  or  Age,  72. 

Bunter  sandstein,  168. 

Augiosperms,  62. 
first  of,  188,  190,*  202. 

continent,  map  of,  73. 
continent,      observations 

Buprestis,  178.* 

in  Tertiary,  209.* 

on,  334. 

Calamites,  108,  128.* 

Animal  kingdom,  47,  48. 

rocks,  73. 

in  Triassic,  167. 

Anisopus,  tracks  of,  171.* 

3alamopsis  Dana?,  210.* 

Anogena,  60. 

Baculites  ovatus,  193.* 

Calcareous  rocks,  21,  24. 

Auoplothere,  214. 

Bad  Lands,  fossils  of,  215. 

Calcite,  18* 

Anthracite,  18,  123. 

Bagshot  beds,  203. 

Callista  Sayana,  212.* 

origin  of,  156,  313. 

Bala  formation,  87. 

Calymene  Blumenbachii,  89.* 

Anthracopal»mon,  132. 
Anticlinal,  41.* 

Basalt,  26,  311. 
Basaltic  columns,  35,*  311.* 

Cambrian,  80. 
Camel,  Tertiary  American,  216 

349 

350 


Canons,  276* 

Coal,   deprived    of    bitumen, 

Crystallizations     during    th» 

Caradoc  sandstone,  87. 

156. 

Appalachian  revolution, 

Carbon,  18. 

formation  of,  135. 

lot). 

Carbonate  of  lime,  18. 

formation,  rocks  of,  122. 

Ctenacanthus  major,  133* 

Carbonic  acid,  IS. 

kinds  of,  18,  123. 

Cteiioids,  50.* 

Carboniferous  Ago,  116. 

plants  of  Richmond,  169.* 

Currents,  oceanic,  285,  286. 

period,  116,  121. 

plants  of  the  Carbonifer- 

Cyathophylloid corals,  88,*  98,* 

Carcharodon  angustidens,  52.* 

ous,  126.* 

111.* 

teeth  of,  21i 

Coccosteus,  113. 

Cyathophyllum          rugosum, 

Carnivores,  first  of,  213. 

3oin-conglomerate,  239.* 

111* 

characteristic  of  Post-ter- 

Colorado, cation  of,  276.* 

Cycads,  61. 

tiary,  in  the  Orient,  231. 

Colunmaria  alveolata,  88.* 

Triussic  and  Jurassic,  Io7.* 

Carpathians,  origin  of,  218. 
Caryocrinua  ornatns,  97.* 

Comprehensive  types,  168,  253. 
Conchilers,  56.* 

Cycloids,  £0.* 
Cyclonema  cancellata,  97.* 

Catastrophes,  origin  of,  332. 
Catopterus  gracilis,  170.* 

Concretions,  33.* 
Conformable  strata,  43.* 

Cyclopteris  linnreiiolia,  168.* 
Cystideans,  57,*  98. 

Catskill  period,  101. 

Conglomerate,  22. 

Cauda-galli  grit,  101. 

Coniiers,  61,  109. 

Decapods,  53.* 

Caves  of  Europe,  Post-tertiary, 

in  Triassic,  167. 

Deer,  fossil,  215,  216. 

230. 

of  Carboniferous,  128. 

Delta  of  Mississippi,  280.* 

Cenozoic  time,  205. 

Connecticut   River  sandstone 

Deltas,  279. 

time,  general  observations 

and  footprints,  164. 

Denudation,  42,*  273,  283,  295, 

on,  £54. 

trap  rocks,  186. 

298. 

Cephalaspis,  113.* 

Continents,    basin-like    sbapc 

Depth,  zones  in,  332. 

Cephalates,  55.* 

of,  9.* 

Dc.-mids,  61,*  109.* 

Cephalopoda,  55.* 

origin  of,  329. 

Detritus,  279,  281. 

of  Mesozoic,  200. 

relations  of,  6,  7,  8,  10. 

Development-  theory,       objec- 

Cestracioiits, 52,*  114,  178. 
Chsetetes  Lycoperdon,  88.* 

Contraction  a  cause  of  change 
of  level,  320. 

tions  to,  115,  257. 
Devonian  age,  104. 

Chain-coral,  97.* 

Coprolites,  183. 

hornstone,  microscopic  or- 

Chalk, 189,  197. 

Coral  islands,  268.* 

ganisms  in,  109.* 

formation  of,  266. 

reef  of  the  Devonian,  105. 

Diamond,  18. 

Champlain  epoch,  219,  224. 

reefs,  266.* 

i  i:,t,:ms.  61.* 

Charcoal,  18. 

Corals,  formation  of,  58.                     formation  of  decosita  bv. 

Chazy  limestone.  86. 

fossil,  88,*  97,*  111,*  131,* 

2fW,  265. 

Cheirotlierium  '         footprints, 

173.* 

Tertiary,  210. 

179.* 

Coralline  crag,  209. 

Dicotyledons,  62. 

Chemung  period,  101. 

Corniierous  limestone,  105. 

Dikes,  30,*  311. 

Chisel,  geological,  344. 

period,  104. 

Binornis,  extinction  of,  241. 

Chlorite  schist,  23. 

Cosmogony,  77,  93,  260. 

Dinothere,  216.* 

Chonetes  mesoloba,  131.* 

Cotopaxi,  volcano  of,  301.* 

Diorite,  26. 

setigera,  112.* 

Crabs,  53.* 

Dip,  39.* 

Cidaris  Blumenbachii,  173.* 

Crassatella  alta,  211.* 

Dipterus,  113.* 

Cinder-cones,  304. 

Crater,  302. 

Dislocated  strata,  38.* 

Cinders,  303. 

Creations  of  species,  92,  116, 

Disturbances    closing    Paleo- 

Cinnamomum, Tertiary,  210.* 

152,  257. 

zoic,  154,  161. 

Claiborne  epoch,  206. 

Crepidula  costata,  212.* 

Dodo,  extinction  of,  241. 

Clathropteris        rectiusculus, 

Cretaceous  period,  163,  188. 

Dolerite,  26,  311. 

168.* 

America,  map  of,  196. 

Dolomite,  19,  25. 

Clay,  20. 

Crevasses,  292. 

Drift,  220. 

Cleavage,  slaty,  36.* 

Cricodus,  51.* 

sands,  32,*  271. 

slaty,  origin  of,  323. 

Crinoidal    limestone,   Subcar- 

scratches,  221.* 

Cliffs,  wear  of,  283* 

boniferous,  121. 

Dromatherium  sylvestre.  172  * 

Climate,  Carboniferous,  138. 

Crinoids,  58* 

Dudley  limestone,  96. 

Cretaceous,  197. 

Jurassic,  173.* 

Dunes,  272. 

Jurassic,  187. 

Primordial.  83.* 

Dynamical  Geology,  262. 

Paleozoic,  149. 

Silurian,  88,*  97.* 

Post-tertiary,  234. 
Tertiary,  219. 

Subcarboniferous,  130.* 
Crocodiles,  195. 

Eagre,  285. 
Earth,  size  and  form  of,  5. 

Clinkstone.    See  PHONOLITE. 

Oocodilus,  first  of,  202. 

general  features  of  surface 

Clinton  group,  94. 

Crustaceans,  53.* 

of,  5. 

Coal  areas  of  Britain  and  Eu 

Cryptogams,  60. 

relation  to  Man,  336. 

rope,  119.* 

Crystalline  rocks,  20. 

Earth's  crust,   general  struc- 

areas of  N.  America,  117.* 

Crystallization    in    metamor- 

ture  of,  1. 

beds,  characters  of,  123. 

phism,  312. 

features,  origin  of,  326,  328. 

beds  of  Triassic.  164. 

of  Azoic  rocks,  75. 

Earthquakes,  origin  of,  324. 

INDEX. 


351 


Ebb-and-flow  structure,  31,  80, 
m 
Echini,  57.* 

Fishes,  first  of  Ganoid  and  Sela- 
chians, or  Devonian,  111.* 
first  Teliost,  188,  191.* 

'Greenland,  glaciers  of,  295. 
Green  Mountains,  emergence 
of,  91. 

Misozoic,  174.* 
Echinodenns,  57.* 

Mesozoic  1,0,*  178,*  194.* 
Fish-spines,  113,*  133.* 

Green-sand,  189. 
Grit,  22. 

Edentates,  Post-tertiary,  232.* 

Flags,  22. 

Ground-pine,  60. 

Elephants   Post-tertiary,  231, 
2.32. 

Flint,  14,  189,  192,  197,  266. 
Flint  arrow-heads,  239. 

Grypluea,  species  of,  174,*  192.* 
Guadaloupe,  human  skeleton 

Tertiary,  216. 

Fluvio  marine  formations,  288. 

of,  2+0* 

Elephas  priinigenius,  231. 
Elevation  of  Alps,  2J3,  213. 
of  Appalachians,  155. 

Folded  rocks,  41,*  74,  156,*  320. 
Footprints.    See  TRACKS. 
Foraminifera,  59.* 

Gulf  of  Mexico,  progress  of,  217. 
Gymnosperms,  til. 
Gypsiferous  formation,  165. 

of  Apennines,  203,  218. 
of  coast  of  Sweden,  212. 

Formation,  28. 
Fossililerous  limestone,  21. 

Gypsum,  95,  125,  165. 
Gyrodus  umbilicus,  51.* 

of  Green  Mountains,  91. 

Fossils,  use  of,  in  determining 

of  Kocky  Mountains,  203, 

the       equivalency      of 

Ilalysites  catenulatus,  97.* 

217. 

strata,  3,  45. 

Hamilton  iormation,  105. 

of   western    South    Ame- 

list of  localities  of,  311. 

period,  101. 

rica,  212. 

number  of  species  of,  252. 

Hammer,  geological,  314.* 

Elevations,  causes  of,  318. 
after  Cretaceous,  203. 

Fragmental  rocks,  20,  22. 
Freestone  of  Portland,  Ct.,  161. 

Harmony  in  the  life  of  an  age, 

after  Paleozoic,  151. 

Fresh  waters,  action  of,  273. 

Hawaii,  volcanoes  of,  SOI,*  304.* 

in  Age  of  Man,  211. 

Fusus  Newberryi,  193.* 

Headou  group,  i03. 

Emsry,  15. 

Heat,  29J. 

Enunons,   fossil    mammal   of 

Ganoids,  51.* 

evidence  of  internal,  29D. 

Triassic    described    by, 

Devonian,  111.* 

Height  of  Aconcagua  peak,  302. 

172. 

Triassic,  170.* 

of  Cotopaxi,  301. 

Enaliosaurs,  135,*  180.* 

Sarnet,  16.* 

of  Illimani,  302. 

Encriuus  liliitbrtnis,  57,*  173.* 

Gasteropods,  56.* 

of  Sorata,  302. 

Eivlo^ens,  62. 
England  in  the  Reptilian  age, 

Genera,  long-lived,  151. 
Genesee  shile,  105. 

Hempstead  beds,  209. 
Herbivores,  first  of,  213. 

201. 

Gsnesis,  77,  93,  260. 

Herculaneum,  309. 

geological  map  of,  120.* 

Geoclinal,  42. 

Heterocercul,  51.* 

Entomostracans,  53.* 

Geography,  progress  in  North 

Himalayas,  origin  of,  203,  218. 

EJOCIIB.  206. 

America,  146,  215,  333. 

Hitchcock,  E.,  tracks  described 

era  in  the  Orient,  218. 

American,  in  Azoic,  76.* 

by,  170.* 

Eo?aurus  Acadianm,  134.* 

in  Carboniferous,  139. 

Holoptychius,113.* 

Ei:iiS'-ta,  60,103,128. 

in  Cretaceous,  196.* 

Holyoke,  311. 

Equivalent  strata,  44. 

in  Devonian,  115. 

llomalonotus,  97.* 

Erosion  by  rivers,  273. 

in  Mesozoic,  193. 

Uomocercal,  51. 

over  continents,  233. 

in  Post-tertiary,  226,  228. 

rocks,  23. 

Erupt.ons  of  volcanoes,  306,  303. 

in  Silurian,  90,  93. 

Hornblende,  16. 

non  volcanic,  310. 

in  Tertiary,  216.* 

Hornstone,  105. 

E'theria  ovata,  163* 

in  Triassic,  181. 

microscopic    remains    in, 

Eituary  formations,  279. 

Geysers,  303. 

103* 

Eurypterus  remipas,  93.* 

Giants'  Causeway,  311. 

Horse,  fossil,  215,  216. 

Exogyra  costata,  192.* 

Glacial  epoch,  219,  220. 

Hudson  period,  85. 

Extermination  of  species,  93, 

Glacier,  great,  of  Switzerland, 

tlywna  spelaea,  2GO. 

150,  203,  202,  256. 
number  of  species  of  plants 

223,  233.* 
regions,  295. 

Hybodus,  species  of,  52  * 
Hydroid  Acalephs,  58,*  82.* 

and  animals  lost  by,  2-il. 

scratches,  221.* 

of  species,  methods  of,  256, 

theory  of  the  drift,  223. 

Ice  of  lakes  and  rivers,  231. 

332. 

Glaciers,  231. 

glacier,  231. 

Glen  Roy,  benches  of,  223. 

Icebergs,  2-3,  286,  236. 

Fasciolaria  buccinoides,  193.* 

Glvptodon,  232.* 

Iceberg  theory  of  the  drift,  223. 

Faults,  41,*  158.* 

Gneiss,  23. 

Ichthyosaurus,  1£0,*  195. 

Favorites  Goldfussi,  111.* 

Gomatites,  first  of,  110. 

Igneous  rocks,  21,  25. 

Niagarensis,  97. 

last  of,  in  Triassic.  175,  200. 

ejections  of  Lake  Superior 

Feldsp  ir,  15. 

Marcellensis,  111.* 

region,  91. 

Ferns,  60. 

Grammysia       Hamiltonensis, 

ejections,  Triassic,  165. 

of  th3  Coal  era,  126.* 

112.* 

Iguanodon,  181,  1!35. 

Fino-al  a  Cave,  301. 

Granite,  23,  25. 

Illinois  coal  area,  117. 

Fiords,  220. 

Graphite,  18,  76. 

Infusorial  beds,  Tertiary,  210. 

Fishes,  50.* 

Graptolites,  82.* 

Ink-bag,  fossil,  176* 

Age  of,  10  1. 

Great  Britain  in  the  Reptilian 

Inoceramus       problematiciu» 

Carboniferous.  133.* 

age,  201. 

192.* 

352 


Insectivores,  Jurassic,  184. 
Insects,  63. 

Life,  general  laws  of  progress  'Megathere,  232.* 
of,  250.                                Mer-de-glace,  292. 

first  of,  107. 

of  Age  of  man,  238.             Mesozoic  time,  162. 

Carboniferous,  133.* 

Life.     See  SPECIES. 

disturbances  and  progress, 

Triassic,  16J.* 

Lignite,  18,  219. 

248. 

Irish  Elk,  230. 

Limestone,  24,  25. 

general    observations  on, 

Iron  ore  beds  of  Azoic,  74.* 

formation  of,  265,  269,  297. 

198. 

mountains  of  Missouri,  74. 
Isopods,  54.* 

Limestones      of      Mississippi 
valley,  143. 

geography  of,  198. 
life  of,  LOO. 

Isotelus  gigas,  89.* 
Itacolumite,  21. 

Lingula  flags,  80. 
Lingulae,  81.* 

Metallic  veins,  £0,  317. 
Metamorphic  rocks,  21,  23. 

Liriodendrom  Meekii,  191.* 

Mctamorphism,    nature     and 

Jackson  epoch,  206. 
Joints  in  rocks,  35.* 

Lithological  Geology,  13. 
Lithostrotion  Canadense,  131.* 

cause  of,  312. 
Azoic,  7ft. 

origin  ol,  3-:*. 
Jurassic  period,  163. 

Llandeilo  flags,  87. 
Llandov  -ry  beds,  96. 

during    the    Appalachian 
revolution,  lid. 

Localities  of   fossils,    list    of, 

Mica,  16. 

Keuper,  166. 

341. 

schist,  23. 

Kilauea,  Ml* 

London  clay,  203. 

Michigan  coal  area,  117. 

Kinssmill  Islands,  263. 

Lorraine  shale,  87. 

Microdon  bellistriatus,  112.* 

Lower  Ileldcrberg,  95. 

Microscopic     organisms,    59,* 

Labradorite,  16. 

Ludlow  group,  U6. 

61,*  263. 

Labyrinthodonts,  179.* 

formation  of  deposits  of, 

Lacustrine  deposits,  ±24.*            Machjerodus,  220. 

265. 

Lake   Champiain  in   l>ost-ter-;  Madagascar,  JEpiornis,  of,  241. 
tiary,  226,  2^7.                   Magnesian  limestone,  19,  25. 

Mind,  Era  of,  226. 
Mineral  coal.    See  COAL 

Meiuphremagog,        Devo- 

Mammals, £0. 

oil,  124. 

nian  coral  reef  of,  105. 
Lakes,  origin  of  great,  148,  247. 

Age  of,  205. 
first  of,  170. 

Miocene,  206. 
Mississippi   River,  completed, 

Lamellibranchs,  56.* 

Jurassic,  183,*  201. 

207. 

Laminated  structure,  21,  31.* 

Mesozoic,  201. 

amount  of  water  of,  274. 

Lamna  elegans,  5.!,*  213. 

Post  tertiary,  230.* 

detritus  of,  279. 

Land-slides,  2s2. 

Tertiary,  213.* 

Missouri  coal  area,  117. 

Lava,  ^6,  303. 

Triassic,  172.* 

iron-mountains  of,  74. 

Lava-cones,  304. 
Layer,  23. 

Man,  Age  of,  236. 
characteristics  of,  236. 

Moa,  extinction  of,  241. 
Mollusks,  49,  54.* 

Lecanocrinus  elegans,  89.* 

fossil,  of  Guadaloupe,  239.* 

Monkeys,  first  of,  236. 

Leguminosites,  lal.* 
Leidy,  J.,    fossil   animals   de- 

place of  origin  of,  240. 
Map  of  coal  region  of  Penn- 

Tertiary, 216. 
Monoclinal,  42. 

scribed  by,  170,*  215. 

sylvania,  118.* 

Monocotyledons,  62. 

Leperditiu,  Ann'a,  81.* 

of  England,  120.* 

Moraines,  294.* 

Lepidodendra,  10S,  127.* 

of  N.  America,  Azoic,  73.* 

Mosaic  cosmogony,  77,  93,  260. 

Lepidodendron        primaevum, 

of  N.  America,  Cretaceous, 

Mosasaur,  195.* 

107.* 

196. 

Mountains,   elevation  of,  218, 

Lepidosteus,  51.* 

of  N.  America,  Tertiary, 

318. 

Leptiena  sericea,  88.* 

21,-.* 

of  Paleozoic  origin,  148. 

transversalis,  97.* 

of  New  York  and  Canada, 

made  after  the  close  of  the 

Leptoenas,  last  of,  174,  200. 

71.* 

Paleozoic,  154. 

Level,  change  of,  in  Greenland, 

of  United  States,  69.* 

made  alter  the  Cretaceoui 

243.                                     Marble,  25. 
changes  of,  in  Age  of  Man,!  Marcellus  shale,  105. 
241.                                     Marine  formations,  287. 

period,  204. 
See  ELEVATIONS. 
Mount  Blanc,  262. 

changes   of,    in    Post-ter-  Marl,  22. 

Ilolyoke,  165,  311. 

tiary,  226,  228,  249. 

Marlite,  22. 

Kea,  301. 

origin  of  changes  of,  318. 

Marsupials,  £0. 

Loa,  £01* 

recent     changes     of,     in 

first  of,  172. 

Kosa  glaciers,  293. 

Eastern  N.  America,  243. 

Jurassic,  184,*  201. 

Tom,  311. 

recent   changes   of,   in   S. 

Post-  tertiary,  233. 

Muck.  265. 

America,  242. 

Massive  structure,  21,  31.* 

Mud-cones,  310. 

recent     changes     of,    in 
Sweden,  212. 

Mastodon.  Post-tertiary,  231.* 
Tertiarv,  216. 

Mud-cracks,  33,  80,  102,  145. 
Muschelkalk,  166. 

Level.    See  ELEVATION. 

Mastodonsaurus,  179  * 

Myriapods,  first  of,  ICO.* 

Lias,  166. 

Mauna.     See  MOUNT. 

. 

Libellula,  177* 

Medina  group,  94. 

Nautilus,  55.* 

Life,  agency  of,  in  rock-making, 

Megaceros  Hibernicus,  230. 
Megalosaur,  181.* 

Nautilus  tribe,  number  of  ex- 
tinct specie*  of,  252. 

INDEX. 


353 


Ser-  Brunswick  coai  area,  117.!Panmotu  Archipelago,  269.        Radiates,  49,  57.* 

Niagara  Falls,  rocks  of,  27,* 
95.* 
group,  94. 

Peat,  formation  of,  263.              Rain-prints,  33,*  145. 
Peccary,  fossil,  215.                    iRaniceps  Lyellii,  134, 
PecopterisStuttgartensis,168.*  Reefs,  coral,  260.* 

period,  94. 

Pemphix  Sueurii,  178.* 

sand,  287,  289. 

River,  gorge  of,  277. 
North  America,  form  of,  9. 

Peutamerus  galeatus,  98.* 
oblongus,  97.* 

Rcgelatioii,  294. 
Reptiles,  50. 

geography  of.     See  GEO- 

Pentremites, first  of,  130.* 

first  of,  134. 

GRAPHY. 

Permian  period,  116,  125. 

Mesozoic,  171  *  178  *  195,* 

Norwich  crag,  209. 

Petraia  Corniculum,  89.* 

201. 

Notidanus  primigenius,  52.* 

Petroleum.  124. 

tracks  of,  171.* 

Nova  Scotia  coal  area,  117. 

Phacops  Bufo,  111.* 

Reptilian  age,  162. 

Nummulites,  59* 

Phascolotheriurn,  183* 

Rhinoceroses,  Tertiary,   215,* 

Nuinmulitic  limestone,  '208. 

Phenogams,  61. 
Phonolite,  304 

216. 
Rhizopods,  59.* 

Occident,  characteristics  of,  5. 

Phyllopods.  82. 

Cretaceous,  190  * 

Ocean,  depression  of,  6,  7. 

Physiographic  Geology,  5. 

formation  of  deposits  by 

effects  of,  283. 

Plants,  47,  60. 

263,  266. 

Oceanic  basin,  origin  of,  329. 
waves,  earthquake,  325. 
Ohio,  coral  reef  of  Falls  of,  105. 

Carboniferous,  126.* 
earliest  marine,  76,  80. 
earliest  terrestrial,  or  De- 

Rhode Island  coal  area,  117. 
Rhynchonella  cuneata,  97.* 
ventricosa,  98.* 

Oil,  mineral,  124. 

vonian,  93,*  107.* 

Rill-marks,  33,*  102,  189. 

Old  red  sandstone,  106. 

Tertiary,  210.* 

Ripple-marks,  33,*  80,  102,  145, 

Oneida  conglomerate,  94. 

Triassic,  167.* 

289. 

Onondaga  limestone,  105. 

Platvceraa  angulatum,  97.* 

Rivers,  action  of,  273. 

Oolite,  25,  166. 
Ophileta  levata,  81.* 

Plesiosaurs,  180,*  195. 
Pleurotomaria       lenticularis, 

of  Paleozoic  origin,  148. 
River  terraces,  225.* 

Orbitqlina  Texana,  191.* 

88* 

Rock,  definition  of,  14. 

Orient,  characteristics  of,  5. 

tabulata,  131.* 

Rocks,  constituents  of,  14. 

Origin  of  speciss.  See  CREATION. 

Pliocene,  206. 

formation  of  sedimentary, 

Oriskany  period,  104. 

Pliosaur,  180. 

296. 

sandstone,  104. 

Podozamites  lauceolatus,  168.* 

kinds  of,  20. 

Orthis  biloba,  97.* 

Polycystines,  5J,*  263. 

of  Mississippi  Valley,  sec 

occidental,  88.* 

Polyps,  58.* 

tion  of  143.* 

testudinaria,  88.* 

Polythalamia,  59* 

of  New  York,  section  ot, 

Orthoceras,  8.).* 

Pompeii,  303. 

66.*  70,*  95,*  96,*  106.* 

last  of,  175,  200. 
Orthoclase,  15. 

Porphyry,  26,  311. 
Portland  (England)  dirt-bed, 

origin  of  Paleozoic,  144. 
thickness  of  Paleozoic,  in 

Osmeroides  Lewesiensis,  194.* 

166. 

North  America,  142,  249. 

Ostracoids,  54,*  82.* 

(Connecticut)     freestone, 

Rocky   Mountains,  origin  of, 

of  Triassic,  163.* 

164. 

198,  203,  217,  249. 

Ostrea  sellseformis,  211.* 
Otozoum  Moodii,  171.* 
Outcrop,  39.* 

Post-tertiary  period,  219. 
changes  of  level,  2  '9,  331. 
general  results  of,  234. 

Mountain  coal  area,  117. 
Rotalia,  59,*  192. 

Ox,  first  of,  216. 

Potsdam  period,  79. 

St.  Lawrence  River  in  the  Poet. 

Oyster,  Tertiary,  211,*  212. 

Primordial  period,  79. 

tertiary,  226,  227. 

Prionastraea  oblonga,  173.* 

Saliferous    group,  of   Britain 

Packing  specimens,  346. 
Palaeaster  Niagarensis,  57.* 

Productus  Rogersi,  131.* 
Protophytes,  60.* 

and  Europe,  166. 
rocks  of  New  York,  95. 

Palaeoniscus  lepidurus,  51.* 

Protozoans,  49,  58,*  190. 

Salina  rocks,  95,  101. 

Freieslebeni,  51,*  133.* 

Pterichthvs,113.« 

Salisbury  craigs,  311. 

Palaeosaurus  Carolinensis,170.* 

Pterodactyl,  181,*  195. 

Salix  Meekii.  191  * 

Paleothere,  214.* 
Paleozoic  time,  78. 

Pterophyllum      graminoides, 

Salt  of  coal  formation,  124. 
of  Salina,  Ac.,  95. 

disturbances  closing,  154. 

Pterooods,  56* 

of  Triassic,  166. 

general    observations  on, 

Pterosaurs,  181.* 

Sand,  20. 

142. 

Pudding  stone,  22. 

Sand-banks,  287,  289. 

Palephemera  mediaeva,  170.* 

?upa  vetusta,  131.* 

Sand-scratches,  273. 

Palisades,  165,  186,  312. 
Palms,  first  of,  188,  190,  202. 

Pyroxene,  16.                               [Sandstones,  22. 
Sapphire,  15. 

Tertiary,  210.* 

Quadrupeds.    See  MAMMAL.       Sassafras  Cretaceum,  191.* 

Palpipespriscus,178.* 
Paludina  Fluviorum,  174.* 

Quarternary.     See    POST-TEK-  Sauropus  primaevus,  134.* 
TIART.                                   Scaphites  larvasformis,  103.* 

Paradoxides  Harlani,  81.*         |  Quartz,  14.*                                 Schist,  schistose  rocks,  21,  23 

Paris  basin,  Tertiary  animals  Quartz  rock,  or  Quartzite,  24.    Schoharie  grit,  104. 
of,  208,  214.*                    iQuercus,  Tertiary,  210.*            \  Scolithus  linear*,  83. 

354 


Stalagmite,  25. 
Star-fishes,  58.* 
Statuary  marble,  25. 
Steatite,  17. 


Scoria,  26 

Sccrpious,  first  of,  130. 

Soouring-rush,  60. 

Seaweeds,  60. 

Section  of  New  York  rocks,  Sti-mariae,  123.' 

70.*  Strata,  delinition  <.f,  28. 

of  the  series  cf  rocks,  66.*          origin  of,  37. 
Sections  of   Paleozoic    rocks,          positions  of,  36,*  43. 
143,*  157,*  15S.*  i  Stratification,  27,*  31.* 

Sedimentary  beds,  formation  Strike,  41.* 

of,  2t)6.  Subcarboniferous  period,  116, 

Selachians,  52.* 

Devonian,  111.* 
Serpentine,  17. 
Shale,  21,  22,  31. 
Sharks,  52.' 


teeth,  52,*  178,  212. 

Sigillariie,  02, 10J. 

Carboniferous,  128.* 
Devonian,  107.* 

Silica,  or  Qu.irtz,  14. 

Sili.-ates,  15. 


gions,  303. 

Subterranean  waters,  281. 
Suffolk  crag,  209. 
Syenite,  23. 

Siliceous    shells,   microscopic,  Syringopom  Maclurii,  111. 

59*,  61,*  263. 

waters  of  Geysers,  303.         Talc,  17. 
Silt,  279.  Talcose  schist,  23. 

Silurian  age,  78.  JTeliost  fishes,  50.* 


Trap,  columnar,  311.* 
Travertine,  21. 
Tree-ferns,  Ii6.* 
Trentou  falls,  period,  85. 

rocks  of,  80. 
Triassi^  period,  163, 161. 

rocks,  origin  of  American, 

185. 

Trigonia  clavellata,  _174.* 
Trigonocarpum        tricuspida- 

tum,  127.* 

121.  Trilobites,  54,*  150. 

Submarine  eruptions,  309.  Devonian,  110.* 

Subsidence   of  coast  of  New          number  of  extinct,  252 
Jersey,  243.  Silurian,  81*  89  *  97.* 

of  Greenland,  recent,  243.  iTufa,  23.  303. 
Subsidences    of    volcanic    re-  Turrilites  catenarus,  193.* 
Turritella  carinata,  211* 
Turtle  of  India,  213. 
Turtles,  Jurassic,  183. 
Tertiary,  216. 


Unconformablc  strata,  43.* 
Under  clays,  122. 
Univalves,  55.* 
CJnstratified  condition,  28.« 


oijjuuiiia  ionaia,  i»a.~                 •  leuosis,  nrst  01.  IBB,  ly-t,*  ~AK, 
Slate,  21,  24.                                           Tertiary,  212. 
Slaty  cleavage,  36,*  323.             Tentacnlltes,  98.* 

upper  Missouri  region.  IOSSL" 
quadrupeds  of,  2lt.* 
Missouri  Tertiary,  207. 

Sloths,   gigantic,   of  Post-ter-  Terrace  epoch.  220.  227. 

L'rsus  spelirus,  2CO. 

tiary,  232.*                          Terraces  on  Connecticut  Iliver, 

Utica  shale,  87. 

Snakes,  first  of,  213.                               225.* 

no  Jurassic,  183.                          of  Scotland.  229. 

Valleys,  formation  of,  274. 

So;-.pstone.  17.                                       origin  of,  227.  228.* 

Veins,  2-3.* 

Solenhoien  lithographic  lime-  Tertiary  period,  206. 

formation  of,  316. 

stone,  166. 

general  results  of,  234. 

Vertebrates,  40,  CO. 

fossils  from,  177. 

in  America.  207. 

first  of,  107,  258. 

Solfataras,  309. 

of  England,  203. 

Vesuvius,  308. 

South  America,  form  of,  9. 
Species,  exterminations  of,  93, 

Tetradecupods,  53.* 
Tetragonolepis,  179.* 

Vicksburp  epoch,  206. 
Vivipara  Fluviorum,  174.* 

150,  2iH),  202,  256.  3*2. 
introduction  of,  149,  256. 
origin  of,  92,  116,  152,  256. 

Thallogens,  60. 
Thanet  sands.  203. 
Thecodonts,  135. 

Volcanoes,  distribution  of,  300. 
nature  of,  301. 

permanency  of,  152. 
Specimens,  on  collecting  and 

Thickness  of  rocks  in  Appa- 
lachian region,  102. 

Water,  action  of,  273. 
Waters,  subterranean,  281. 

packing,  346. 
Sphcnopteris  laxus.  107.* 

of  stratified  rocks,  44. 
Thrissops,  51.* 

freezing  and  frozen,  290. 
Waves,  action  of,  283. 

Gravenhorstii,  127.* 

Tidal  currents,  285. 

Wealdcn,  1C6. 

Spicules  of  Sponges,  58,  110,* 

Time,  length  of  geological,  244, 

Wcnlock  limestone,  96. 

192. 

215. 

Whales,  first  of,  213. 

Spiders,  first  of,  177.* 

Time-ratios,  145,  198,  243. 

Wind-drift  structure,  32.* 

Spinax  Blainvillii,  52.* 

Titanothere,  215.* 

Woolwich  beds,  203. 

Spine  of  a  fish,  113*133* 

Tourmaline,  17.* 

Worms,  53,*  83. 

Spirifer  cameratus,  131.* 

Trarhvte,  26. 

macropleurus,  98.* 

Tracks  of  birds,  172.* 

Xylobius  Sigillarise,  132* 

mucronatus,  112.* 

Cheirotherium,  179* 

Niagarensis,  97.* 

of  insects,  170* 

Yoldia  li  mat  ula,  212.* 

Walcotti,  174.* 

of    reptiles    in    Carboni- 

Yorktown epoch,  206. 

Spiriiers,  last  of,  174,*  200. 

ferous,  134.* 

Sponge,  Cretaceous,  192.* 
Sponges,  58. 

of  reptiles,  Triassic,  171. 
of  Trilobites,  81.* 

Zamia,  62. 

leaf  of,  167.* 

Sponge-spicules,  58,  110,  192. 
in  hornstone,  110.* 

Transportation  by  rivers,  277. 
Trap,  26. 

Zaphrenti3  bilateralis,  97  * 
Rafinesquii,  111.* 

Stag  family,  first  of,  236. 
Stalactites,  25. 

of  Connecticut  valley,  4c., 
165. 

Zeacrinus  elegans,  131.* 
Zeuglodon,  214. 

'' 


UNIVERSITY  OF  CALIFORNIA,  LOS  ANGELES 

THE  UNIVERSITY  LIBRARY 
This  book  is  DUE  on  the  last  date  stamped  below 


OGT  1 1  WS 
'JUL  30 


uuT  7  _  1947, 
OCT2-  1974 


TheR 


LPH  D.  REED  LIBRARY 


DElf  \RTVENT  OF  GEOLOGY 

UNIVIRSITY  of  CALIFORNL 

I, OS  ANGELES,  CALIF. 


BY  E.  HUNT. 

A  new  work,  just  published,  based  upon  an  original  and  practical  plan.  It 
comprises  representative  selections  from  the  best  authors,  also  list  of  contem- 
poraneous writers  and  their  principal  works. 


1  H 


UC  SOUTHERN  REGIONAL  LIB 


QE26 


Dana  '- 


A   text-book    Of 

geology. 


QB26 
D19ml 


Co.'s  Publications. 


;RMAN  COURSE. 

isquelle's  system. 

Woodbury's  Eclectic  German  Reader 
Woodbury's  German  English  Reader. 
Glaubensklees  German  Reader. 
Glaubensklee's  Synthetic    German 
Grammar. 


Sanders'  German  and  English  Primer. 
Mess  &>•  Sanders'  Phonetic  Speller. 
Mess  <5r»  Sanders'  German  Speller  and 
Reader. 

\NISH    READERS. 

MANTILLA. 

Libro  de  Lecture.    No.  a. 
;ura.    No.  3. 
.ols  in  the  West  India  Islands,  Mexico, 

E  K  . 

ek  Grammar. 

ementary  Greek  Grammar. 

ction. 

A  new  primary  book. 


3    TINT    HVETTSXO 
.  LOOMIS. 


ruction  in  Vocal  Music  for  Common 
Four  Books. 


3OOZK1S. 

instructed  for  definite  results  in  recita- 
f  topical  reviews.    Fully  illustrated. 

lass  book  of  English  derivative  words 
,  Analyzing,  Defining,  Synonyms,  and 

ementary  and  progressive  Series  in  Six 
abridgment  of  The  Inorganic  Chem- 


CATHCART'S    PRIMARY   SPEAKER  ;   suited   to   the   requirements   of    Common 
Schools. 

TOWNSEND'S  COMMERCIAL  LAW. 


^T"  THE  ILLUSTRATED  CATALOGUE,  descriptive  of  THE  AMER- 
ICAN EDUCATIONAL  SERIES  OF  SCHOOL  AND  COLLEGE  TEXT-BOOKS,  and  THE  EDU- 
CATIONAL REPORTER,  a  handsome  publication  full  of  useful  information,  mailed 
free  to  teachers. 

IVISON,   BLAKEMAN,    TAYLOR  &  CO., 

PUBLISHERS, 

138  &  140  GRAND  STREET,  NEW  YORK. 
133  &  135  STATE  STREET,  CHICAGO. 


